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Greetings!

Please can anyone help me by reviewing this code, and letting me know if there are any major issues?

Full code:

// SPDX-License-Identifier: Unlicensed

pragma solidity 0.8.9;


interface IBEP20 {
    
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external pure returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterward:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}


/**
 * @dev Implementation of the DEX interfaces.
 * Default configuration is for the PancakeSwap finance.
 * PancakeSwap is a leading decentralized exchange on the binance smart chain.
 * Refer below link for further details.
 * https://docs.pancakeswap.finance/code/smart-contracts/pancakeswap-exchange/router-v2
 * 
 * WETH returns the canonical address for WBNB token (ETH = BNB). 
 */
 
// pragma solidity >=0.5.0;

interface IPancakeswapV2Factory {
    event PairCreated(address indexed token0, address indexed token1, address pair, uint);

    function feeTo() external view returns (address);
    function feeToSetter() external view returns (address);

    function getPair(address tokenA, address tokenB) external view returns (address pair);
    function allPairs(uint) external view returns (address pair);
    function allPairsLength() external view returns (uint);

    function createPair(address tokenA, address tokenB) external returns (address pair);

    function setFeeTo(address) external;
    function setFeeToSetter(address) external;
}


// pragma solidity >=0.5.0;

interface IPancakeswapV2Pair {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external pure returns (string memory);
    function symbol() external pure returns (string memory);
    function decimals() external pure returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);
    function PERMIT_TYPEHASH() external pure returns (bytes32);
    function nonces(address owner) external view returns (uint);

    function permit(
        address owner, 
        address spender, 
        uint value, 
        uint deadline, 
        uint8 v, 
        bytes32 r, 
        bytes32 s
    ) external;

    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint);
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (
        uint112 reserve0, 
        uint112 reserve1, 
        uint32 blockTimestampLast
    );
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
    function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}


// pragma solidity >=0.6.2;

interface IPancakeswapV2Router01 {
    function factory() external pure returns (address);
    function WETH() external pure returns (address);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint amountADesired,
        uint amountBDesired,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB, uint liquidity);
    function addLiquidityETH(
        address token,
        uint amountTokenDesired,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external payable returns (uint amountToken, uint amountETH, uint liquidity);
    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETH(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountToken, uint amountETH);
    function removeLiquidityWithPermit(
        address tokenA,
        address tokenB,
        uint liquidity,
        uint amountAMin,
        uint amountBMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountA, uint amountB);
    function removeLiquidityETHWithPermit(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountToken, uint amountETH);
    function swapExactTokensForTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapTokensForExactTokens(
        uint amountOut,
        uint amountInMax,
        address[] calldata path,
        address to,
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactETHForTokens(
        uint amountOutMin, 
        address[] calldata path, 
        address to, 
        uint deadline
    ) external payable returns (uint[] memory amounts);
    function swapTokensForExactETH(
        uint amountOut, 
        uint amountInMax, 
        address[] calldata path, 
        address to, uint deadline
    ) external returns (uint[] memory amounts);
    function swapExactTokensForETH(
        uint amountIn, 
        uint amountOutMin, 
        address[] calldata path, 
        address to, 
        uint deadline
    ) external returns (uint[] memory amounts);
    function swapETHForExactTokens(
        uint amountOut, 
        address[] calldata path, 
        address to, 
        uint deadline
    ) external payable returns (uint[] memory amounts);
    function quote(
        uint amountA, 
        uint reserveA, 
        uint reserveB
    ) external pure returns (uint amountB);
    function getAmountOut(
        uint amountIn, 
        uint reserveIn, 
        uint reserveOut
    ) external pure returns (uint amountOut);
    function getAmountIn(
        uint amountOut, 
        uint reserveIn, 
        uint reserveOut
    ) external pure returns (uint amountIn);
    function getAmountsOut(
        uint amountIn, 
        address[] calldata path
    ) external view returns (uint[] memory amounts);
    function getAmountsIn(
        uint amountOut, 
        address[] 
        calldata 
        path
    ) external view returns (uint[] memory amounts);
}


// pragma solidity >=0.6.2;

interface IPancakeswapV2Router02 is IPancakeswapV2Router01 {
    function removeLiquidityETHSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline
    ) external returns (uint amountETH);
    function removeLiquidityETHWithPermitSupportingFeeOnTransferTokens(
        address token,
        uint liquidity,
        uint amountTokenMin,
        uint amountETHMin,
        address to,
        uint deadline,
        bool approveMax, uint8 v, bytes32 r, bytes32 s
    ) external returns (uint amountETH);
    function swapExactTokensForTokensSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
    function swapExactETHForTokensSupportingFeeOnTransferTokens(
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external payable;
    function swapExactTokensForETHSupportingFeeOnTransferTokens(
        uint amountIn,
        uint amountOutMin,
        address[] calldata path,
        address to,
        uint deadline
    ) external;
}


/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
 
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with a custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with a custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with a custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}


/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects
     * -interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi
     * -encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have a BNB balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}


/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions, the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return payable (msg.sender);
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode 
              //- see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}


/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}


/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address private _owner;
    address private _previousOwner;
    uint256 private _lockTime;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(_owner == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

     /**
     * @dev Leaves the contract without an owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() external virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) external virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}


/**
 * @dev Implementation of the {IBEP20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism, see {BEP20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup, see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 */
contract CURIOSITY is Context, IBEP20, Ownable, ReentrancyGuard {
    using SafeMath for uint256;
    using Address for address;

    mapping (address => uint256) private _rOwned;
    mapping (address => uint256) private _tOwned;
    mapping (address => mapping (address => uint256)) private _allowances;

    mapping (address => bool) private _isExcludedFromFee;

    mapping (address => bool) private _isExcluded;
    address[] private _excluded;
   
    uint256 private constant MAX = ~uint256(0);
    uint256 private constant _tTotal = 225 * 10**6 * 10**18;
    uint256 private _rTotal = (MAX - (MAX % _tTotal));
    uint256 private _tFeeTotal;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    string private constant _name = "Curiosity";
    string private constant _symbol = "CURI";
    uint8 private constant _decimals = 18;
    
    /**
     * @dev Percentage of the static reflection fee.
     */        
    uint256 public _taxFee = 7;
    uint256 private _previousTaxFee = _taxFee;

    /**
     * @dev Percentage of the liquidity fee.
     */           
    uint256 public _liquidityFee = 1;
    uint256 private _previousLiquidityFee = _liquidityFee;

    /**
     * @dev Percentage of the auto burn fee.
     */   
    uint256 public _burnFee = 1;
    address public burnAddress = 0x000000000000000000000000000000000000dEaD; 
    uint256 private _previousBurnFee = _burnFee;

    /**
     * @dev Percentage of the marketing, development, and team fee.
     */   
    uint256 public _developmentFee = 1;
    address public developmentWallet = 0x0C9186611Cfc19B11D712112fE33E86BF3eB9678;
    uint256 private _previousDevelopmentFee = _developmentFee;

    IPancakeswapV2Router02 public pancakeswapV2Router;
    address public pancakeswapV2Pair;
    
    bool inSwapAndLiquify;
    bool public swapAndLiquifyEnabled = false;

    /**
     * @dev The maximum transaction amount to minimize and break the impact of 
     * Whale actions.
     */       
    uint256 public _maxTxAmount = 1 * 10**6 * 10**18;
    
    /**
     * @dev The amount of token sell to add to the liquidity.
     */     
    uint256 public numTokensSellToAddToLiquidity = 50000 * 10**18;
    
    event MinTokensBeforeSwapUpdated(uint256 minTokensBeforeSwap);
    event SwapAndLiquifyEnabledUpdated(bool enabled);
    event SwapAndLiquify(
        uint256 tokensSwapped,
        uint256 ethReceived,
        uint256 tokensIntoLiquidity
    );
    
    modifier lockTheSwap {
        inSwapAndLiquify = true;
        _;
        inSwapAndLiquify = false;
    }
    
    constructor () {
        _rOwned[_msgSender()] = _rTotal;
        
        IPancakeswapV2Router02 _pancakeswapV2Router = IPancakeswapV2Router02(
            0xD99D1c33F9fC3444f8101754aBC46c52416550D1
        );
         // Create a pancakeswap pair for this new token
        pancakeswapV2Pair = IPancakeswapV2Factory(_pancakeswapV2Router.factory())
            .createPair(address(this), _pancakeswapV2Router.WETH());

        // set the rest of the contract variables
        pancakeswapV2Router = _pancakeswapV2Router;
        
        //exclude owner and this contract from fee
        _isExcludedFromFee[owner()] = true;
        _isExcludedFromFee[address(this)] = true;
        _isExcludedFromFee[burnAddress] = true;
        
        emit Transfer(address(0), _msgSender(), _tTotal);
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() external pure returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the token symbol.
     */
    function symbol() external pure returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the token decimals.
     */
    function decimals() external pure returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IBEP20-totalSupply}.
     */
    function totalSupply() external pure override returns (uint256) {
        return _tTotal;
    }

    /**
     * @dev See {IBEP20-balanceOf}.
     */
    function balanceOf(address account) public view override returns (uint256) {
        if (_isExcluded[account]) return _tOwned[account];
        return tokenFromReflection(_rOwned[account]);
    }

    /**
     * @dev See {IBEP20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - The caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) external override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    /**
     * @dev See {IBEP20-allowance}.
     */
    function allowance(address owner, address spender) external view override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IBEP20-approve}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) external override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    /**
     * @dev See {IBEP20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP.
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - The caller must have an allowance for `sender`'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    )
        external
        override
        returns (bool) 
    {
        _transfer(sender, recipient, amount);
        _approve(
            sender,
            _msgSender(),
            _allowances[sender][_msgSender()].sub(amount, "BEP20: transfer amount exceeds allowance")
        );
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as mitigation for
     * problems described in {IBEP20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(
        address spender, 
        uint256 addedValue
    ) 
        external 
        virtual 
        returns (bool) 
    {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as mitigation for
     * problems described in {IBEP20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have an allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(
        address spender,
        uint256 subtractedValue
    ) 
        external
        virtual 
        returns (bool) 
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].sub(subtractedValue, "BEP20: decreased allowance below zero")
        );
        return true;
    }

    function isExcludedFromReward(address account) external view returns (bool) {
        return _isExcluded[account];
    }

    function totalFees() external view returns (uint256) {
        return _tFeeTotal;
    }

	function totalBurned() external view returns (uint256) {
		return balanceOf(burnAddress);
	}
	
    function tokenFromReflection(uint256 rAmount) public view returns(uint256) {
        require(rAmount <= _rTotal, "Amount must be less than total reflections");
        uint256 currentRate =  _getRate();
        return rAmount.div(currentRate);
    }

    function excludeFromReward(address account) external onlyOwner() {
        require(account != 0x10ED43C718714eb63d5aA57B78B54704E256024E, 'We can not exclude Pancake router.');
        require(!_isExcluded[account], "Account is already excluded");
        if(_rOwned[account] > 0) {
            _tOwned[account] = tokenFromReflection(_rOwned[account]);
        }
        _isExcluded[account] = true;
        _excluded.push(account);
    }

    function includeInReward(address account) external onlyOwner() {
        require(_isExcluded[account], "Account is not excluded");
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (_excluded[i] == account) {
                _excluded[i] = _excluded[_excluded.length - 1];
                _tOwned[account] = 0;
                _isExcluded[account] = false;
                _excluded.pop();
                break;
            }
        }
    }

    function _transferBothExcluded(address sender, address recipient, uint256 tAmount) private {
        (uint256 rAmount, 
        uint256 rTransferAmount, 
        uint256 rFee, 
        uint256 tTransferAmount, 
        uint256 tFee, 
        uint256 tLiquidity
        ) = _getValues(tAmount);
        _tOwned[sender] = _tOwned[sender].sub(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);        
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }
    
     //to receive BNB from pancakeswapV2Router when swapping
    receive() external payable {}

    function _reflectFee(uint256 rFee, uint256 tFee) private {
        _rTotal = _rTotal.sub(rFee);
        _tFeeTotal = _tFeeTotal.add(tFee);
    }

    function _getValues(
        uint256 tAmount
    ) 
        private view returns(uint256, uint256, uint256, uint256, uint256, uint256) {
        (uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getTValues(tAmount);
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee) = _getRValues(
            tAmount, 
            tFee, 
            tLiquidity, 
            _getRate()
        );
        return 
        (
            rAmount, 
            rTransferAmount, 
            rFee, 
            tTransferAmount, 
            tFee, 
            tLiquidity
        );
    }

    function _getTValues(uint256 tAmount) private view returns (uint256, uint256, uint256) {
        uint256 tFee = calculateTaxFee(tAmount);
        uint256 tLiquidity = calculateLiquidityFee(tAmount);
        uint256 tTransferAmount = tAmount.sub(tFee).sub(tLiquidity);
        return (tTransferAmount, tFee, tLiquidity);
    }

    function _getRValues(
        uint256 tAmount, 
        uint256 tFee, 
        uint256 tLiquidity, 
        uint256 currentRate
    ) private pure returns (uint256, uint256, uint256) {
        uint256 rAmount = tAmount.mul(currentRate);
        uint256 rFee = tFee.mul(currentRate);
        uint256 rLiquidity = tLiquidity.mul(currentRate);
        uint256 rTransferAmount = rAmount.sub(rFee).sub(rLiquidity);
        return (rAmount, rTransferAmount, rFee);
    }

    function _getRate() private view returns(uint256) {
        (uint256 rSupply, uint256 tSupply) = _getCurrentSupply();
        return rSupply.div(tSupply);
    }

    function _getCurrentSupply() private view returns(uint256, uint256) {
        uint256 rSupply = _rTotal;
        uint256 tSupply = _tTotal;      
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (_rOwned[_excluded[i]] > rSupply || _tOwned[_excluded[i]] > tSupply) return (
                _rTotal, 
                _tTotal
            );
            rSupply = rSupply.sub(_rOwned[_excluded[i]]);
            tSupply = tSupply.sub(_tOwned[_excluded[i]]);
        }
        if (rSupply < _rTotal.div(_tTotal)) return (_rTotal, _tTotal);
        return (rSupply, tSupply);
    }
    
    function _takeLiquidity(uint256 tLiquidity) private {
        uint256 currentRate =  _getRate();
        uint256 rLiquidity = tLiquidity.mul(currentRate);
        _rOwned[address(this)] = _rOwned[address(this)].add(rLiquidity);
        if(_isExcluded[address(this)])
            _tOwned[address(this)] = _tOwned[address(this)].add(tLiquidity);
    }
    
    function calculateTaxFee(uint256 _amount) private view returns (uint256) {
        return _amount.mul(_taxFee).div(
            10**2
        );
    }

    function calculateLiquidityFee(uint256 _amount) private view returns (uint256) {
        return _amount.mul(_liquidityFee).div(
            10**2
        );
    }
    
    function removeAllFee() private {
        _taxFee = 0;
        _liquidityFee = 0;
        _burnFee = 0;
        _developmentFee = 0;
    }
    
    function restoreAllFee() private {
        _taxFee = 7;
        _liquidityFee = 1;
        _burnFee = 1;
        _developmentFee = 1;
    }
    
    function isExcludedFromFee(address account) external view returns(bool) {
        return _isExcludedFromFee[account];
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(address owner, address spender, uint256 amount) private {
        require(owner != address(0), "BEP20: approve from the zero address");
        require(spender != address(0), "BEP20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `sender` / `from` cannot be the zero address.
     * - `recipient` / `to` cannot be the zero address.
     * - `sender` / `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,  // sender
        address to,  // recipient
        uint256 amount
    ) private {
        require(from != address(0), "BEP20: transfer from the zero address");
        require(to != address(0), "BEP20: transfer to the zero address");
        require(amount > 0, "Transfer amount must be greater than zero");

        // is the token balance of this contract address over the min number of
        // tokens that we need to initiate a swap + liquidity lock?
        // also, don't get caught in a circular liquidity event.
        // also, don't swap & liquify if sender is pancakeswap pair.
        uint256 contractTokenBalance = balanceOf(address(this));        
        bool overMinTokenBalance = contractTokenBalance >= numTokensSellToAddToLiquidity;
        if (
            overMinTokenBalance &&
            !inSwapAndLiquify &&
            from != pancakeswapV2Pair &&
            swapAndLiquifyEnabled
        ) {
            contractTokenBalance = numTokensSellToAddToLiquidity;
            //add liquidity
            swapAndLiquify(contractTokenBalance);
        }
        
        //transfer amount, it will take tax, burn, liquidity fee
        _tokenTransfer(from,to,amount);
    }

    function swapAndLiquify(uint256 contractTokenBalance) private lockTheSwap {
        // split the contract balance into halves
        uint256 half = contractTokenBalance.div(2);
        uint256 otherHalf = contractTokenBalance.sub(half);

        // capture the contract's current BNB balance.
        // this is so that we can capture exactly the amount of BNB that the
        // swap creates, and does not make the liquidity event include any BNB that
        // has been manually sent to the contract
        uint256 initialBalance = address(this).balance;

        // swap tokens for BNB
        // this breaks the BNB -> HATE swap when swap+liquify is triggered
        swapTokensForEth(half); 

        // how much BNB did we just swap into?
        uint256 newBalance = address(this).balance.sub(initialBalance);

        // add liquidity to Pancakeswap
        addLiquidity(otherHalf, newBalance);
        
        emit SwapAndLiquify(half, newBalance, otherHalf);
    }

    function swapTokensForEth(uint256 tokenAmount) private {
        // generate the pancakeswap pair path of token -> weth
        address[] memory path = new address[](2);
        path[0] = address(this);
        path[1] = pancakeswapV2Router.WETH();

        _approve(address(this), address(pancakeswapV2Router), tokenAmount);

        // make the swap
        pancakeswapV2Router.swapExactTokensForETHSupportingFeeOnTransferTokens(
            tokenAmount,
            0, // accept any amount of BNB
            path,
            address(this),
            block.timestamp
        );
    }

    function addLiquidity(uint256 tokenAmount, uint256 ethAmount) private {
        // approve token transfer to cover all possible scenarios
        _approve(address(this), address(pancakeswapV2Router), tokenAmount);

        // add the liquidity
        pancakeswapV2Router.addLiquidityETH{value: ethAmount}(
            address(this),
            tokenAmount,
            0, // slippage is unavoidable
            0, // slippage is unavoidable
            address(this),
            block.timestamp
        );
    }

    //this method is responsible for taking all fee, if takeFee is true
    function _tokenTransfer(address sender, address recipient, uint256 amount) private {
        if(_isExcludedFromFee[sender] || _isExcludedFromFee[recipient]){
            removeAllFee();
        }
        else{
            require(amount <= _maxTxAmount, "Transfer amount exceeds the maxTxAmount.");
        }
        
        //Calculate burn amount and development amount
        uint256 burnAmt = amount.mul(_burnFee).div(100);
        uint256 developmentAmt = amount.mul(_developmentFee).div(100);

        if (_isExcluded[sender] && !_isExcluded[recipient]) {
            _transferFromExcluded(sender, recipient, (amount.sub(burnAmt).sub(developmentAmt)));
        } else if (!_isExcluded[sender] && _isExcluded[recipient]) {
            _transferToExcluded(sender, recipient, (amount.sub(burnAmt).sub(developmentAmt)));
        } else if (_isExcluded[sender] && _isExcluded[recipient]) {
            _transferBothExcluded(sender, recipient, (amount.sub(burnAmt).sub(developmentAmt)));
        } else {
            _transferStandard(sender, recipient, (amount.sub(burnAmt).sub(developmentAmt)));
        }
        
        //Temporarily remove fees to transfer to burn address and development wallet
        _taxFee = 0;
        _liquidityFee = 0;

        //Send transfers to burn address and development wallet
        _transferStandard(sender, burnAddress, burnAmt);
        _transferStandard(sender, developmentWallet, developmentAmt);

        //Restore tax and liquidity fees
        _taxFee = _previousTaxFee;
        _liquidityFee = _previousLiquidityFee;


        if(_isExcludedFromFee[sender] || _isExcludedFromFee[recipient])
            restoreAllFee();
    }

    function _transferStandard(address sender, address recipient, uint256 tAmount) private {
        (
            uint256 rAmount, 
            uint256 rTransferAmount, 
            uint256 rFee, 
            uint256 tTransferAmount, 
            uint256 tFee, 
            uint256 tLiquidity
        ) = _getValues(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _transferToExcluded(address sender, address recipient, uint256 tAmount) private {
        (
            uint256 rAmount, 
            uint256 rTransferAmount, 
            uint256 rFee, 
            uint256 tTransferAmount, 
            uint256 tFee, 
            uint256 tLiquidity
        ) = _getValues(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);           
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _transferFromExcluded(address sender, address recipient, uint256 tAmount) private {
        (
            uint256 rAmount, 
            uint256 rTransferAmount, 
            uint256 rFee, 
            uint256 tTransferAmount, 
            uint256 tFee, 
            uint256 tLiquidity
        ) = _getValues(tAmount);
        _tOwned[sender] = _tOwned[sender].sub(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);   
        _takeLiquidity(tLiquidity);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    /**
     * @dev The owner can withdraw BNB collected in the contract from `swapAndLiquify`
     * or if someone sends BNB directly to the contract.
     * 
     * The swapAndLiquify function converts half of the contractTokenBalance tokens to BNB. 
     * For every swapAndLiquify function call, a small amount of BNB remains in the contract. 
     * This amount grows over time with the swapAndLiquify function being called throughout the life 
     * of the contract.  
     */
    function withdrawBalanceBNB(
        address payable recipient, 
        uint256 amount
    ) external onlyOwner nonReentrant{
        require(amount <= address(this).balance, "BEP20: amount should not exceed the contract balance");
        recipient.transfer(amount);
    }

    /**
     * @dev The owner can exclude specific accounts from Fees.
     */   
    function excludeFromFee(address account) external onlyOwner {
        _isExcludedFromFee[account] = true;
    }

     /**
     * @dev The owner can include specific accounts in Fees.
     */           
    function includeInFee(address account) external onlyOwner {
        _isExcludedFromFee[account] = false;
    }
    
    /**
     * @dev Call this function to disable all Fees.
     * It will be necessary during the Presale stage.
     */
    function disableAllFees() external onlyOwner() {
        _taxFee = 0;
        _previousTaxFee = _taxFee;
        _liquidityFee = 0;
        _previousLiquidityFee = _liquidityFee;
        _burnFee = 0;
        _previousBurnFee = _burnFee;
        _developmentFee = 0;
        _previousDevelopmentFee = _developmentFee;
    }

    /**
     * @dev Call this function to enable Fees after finalizing the Presale.
     */
    function enableAllFees() external onlyOwner() {
        _taxFee = 7;
        _previousTaxFee = _taxFee;
        _liquidityFee = 1;
        _previousLiquidityFee = _liquidityFee;
        _burnFee = 1;
        _previousBurnFee = _burnFee;
        _developmentFee = 1;
        _previousDevelopmentFee = _developmentFee;
        inSwapAndLiquify = true;
        emit SwapAndLiquifyEnabledUpdated(true);
    }

    /**
     * @dev Call this function to change burnFee to zero percent upon a certain amount 
     * of tokens are burned.
     */
    function stopAutoBurn() external onlyOwner() {
        _burnFee = 0;
        _previousBurnFee = _burnFee;
    }

    /**
     * @dev Update the Router address if Pancakeswap upgrades to a newer version.
     */
    function setRouterAddress(address newRouter) external onlyOwner {
        IPancakeswapV2Router02 _newPancakeRouter = IPancakeswapV2Router02(newRouter);
        pancakeswapV2Pair = IPancakeswapV2Factory(_newPancakeRouter.factory()).createPair(
            address(this), 
            _newPancakeRouter.WETH()
        );
        pancakeswapV2Router = _newPancakeRouter;
    }    
    
    /**
     * @dev Update the amount of 'numTokensSellToAddToLiquidity'.
     */
    function setNumTokensSellToAddToLiquidity(uint256 newAmount) external onlyOwner() {
        numTokensSellToAddToLiquidity = newAmount;
    }
    
    /**
     * @dev Call this function if required to set a different Development wallet address.
     */
    function setDevelopmentWallet(address newWallet) external onlyOwner() {
        developmentWallet = newWallet;
    }

    /**
     * @dev Call this function to change the Max transaction amount.
     * Adjusting of 'maxTxAmount' will be required during the initial stage.
     */      
    function setMaxTxAmount(uint256 newAmount) external onlyOwner() {
        _maxTxAmount = newAmount;
    }

    /**
     * @dev Call this function to enable Swap and Liquify.
     */  
    function setSwapAndLiquifyEnabled(bool _enabled) external onlyOwner {
        swapAndLiquifyEnabled = _enabled;
        emit SwapAndLiquifyEnabledUpdated(_enabled);
    }
}

Mainly I have doubts about the following,

How I used "abstract contract ReentrancyGuard"
Requirement of SafeMath on v.0.8.9
"addLiquidity" function
"withdrawBalance" function

It would be awesome if anyone could help me with these.

If you use this code with pancake I think you will have problems. You renamed the functions of the router, replacing "ETH" with "BNB". This probably will cause problems because pancake code has ETH not BNB word

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Oh!...
@FreezyEx The reason I change that is on page no 19 of, https://questos.net/files/audit_questos.pdf

But you must be correct according to the Pancakeswap website!

Thank you for correcting me.

@FreezyEx Could you please share your thoughts about these codes if you have time?

You have previousFees but you never use them.

Here I can't understand why inSwapAndLiquify is set to true, It should be false by default

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By default, that function is not enabled.

    bool public swapAndLiquifyEnabled = false;

I am going to call the "disableAllFees" function before the presale, and once the presale is finished, I am going to call the "enableAllFees" function.

Is it needs to be corrected like this?.

    /**
     * @dev Call this function to disable all Fees.
     * It will be necessary during the Presale stage.
     */
    function disableAllFees() external onlyOwner() {
        _taxFee = 0;
        _previousTaxFee = _taxFee;
        _liquidityFee = 0;
        _previousLiquidityFee = _liquidityFee;
        _burnFee = 0;
        _previousBurnFee = _burnFee;
        _developmentFee = 0;
        _previousDevelopmentFee = _developmentFee;
        inSwapAndLiquify = false;
        emit SwapAndLiquifyEnabledUpdated(false);
    }

    /**
     * @dev Call this function to enable Fees after finalizing the Presale.
     */
    function enableAllFees() external onlyOwner() {
        _taxFee = 7;
        _previousTaxFee = _taxFee;
        _liquidityFee = 1;
        _previousLiquidityFee = _liquidityFee;
        _burnFee = 1;
        _previousBurnFee = _burnFee;
        _developmentFee = 1;
        _previousDevelopmentFee = _developmentFee;
        inSwapAndLiquify = false;
        emit SwapAndLiquifyEnabledUpdated(false);
    }

inSwapAndLiquify is pretty useless in these functions. I suggest to remove it

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Thank you very much for sharing your suggestions with me.