BEP-20 - how to add Tax fees when token is transfer?

Full Source: This token only deduct tax when selling on dex and tax goes to specific address and the transfer doesn't take any fee.

How to add fee when token was transfer? And fees will go to specific address.

 * @dev Moves `amount` of tokens from `sender` to `recipient`.
 * This 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` cannot be the zero address.
 * - `recipient` cannot be the zero address.
 * - `sender` must have a balance of at least `amount`.
function _transfer(
    address sender,
    address recipient,
    uint256 amount
) internal virtual {
    require(sender != address(0), "ERC20: transfer from the zero address");
    require(recipient != address(0), "ERC20: transfer to the zero address");

    uint256 senderBalance = _balances[sender];
    require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");

    unchecked {
        _balances[sender] = senderBalance.sub(amount);
    bool takeFee = true;
    if (_isExcludedFromFee[sender]) {
        takeFee = false;
        uint256 taxFee = amount.mul(dexTaxFee).div(10000);
        _balances[taxAddress] = _balances[taxAddress].add(taxFee);
        emit Transfer(sender, taxAddress, taxFee);
        amount = amount.sub(taxFee);
    _balances[recipient] = _balances[recipient].add(amount);
    emit Transfer(sender, recipient, amount);

I see that you still did not get any reply. I was soling the same issue now and I found this solution.. Hopefully it will help you

contract TransfertTokenAndPercentageToTargetAddress{

    // pay 1% of all transactions to target address
    address payable target = ENTERANADDRESSHERE;

    // state variables for your token to track balances and to test
    mapping (address => uint) public balanceOf;
    uint public totalSupply;

    // create a token and assign all the tokens to the creator to test
    constructor(uint _totalSupply) public {
        totalSupply = _totalSupply;
        balanceOf[msg.sender] = totalSupply;

    // the token transfer function with the addition of a 1% share that
    // goes to the target address specified above
    function transfer(address _to, uint amount) public {

        // calculate the share of tokens for your target address
        uint shareForX = amount/100;

        // save the previous balance of the sender for later assertion
        // verify that all works as intended
        uint senderBalance = balanceOf[msg.sender];
        // check the sender actually has enough tokens to transfer with function 
        // modifier
        require(senderBalance >= amount, 'Not enough balance');
        // reduce senders balance first to prevent the sender from sending more 
        // than he owns by submitting multiple transactions
        balanceOf[msg.sender] -= amount;
        // store the previous balance of the receiver for later assertion
        // verify that all works as intended
        uint receiverBalance = balanceOf[_to];

        // add the amount of tokens to the receiver but deduct the share for the
        // target address
        balanceOf[_to] += amount-shareForX;
        // add the share to the target address
        balanceOf[target] += shareForX;

        // check that everything works as intended, specifically checking that
        // the sum of tokens in all accounts is the same before and after
        // the transaction. 
        assert(balanceOf[msg.sender] + balanceOf[_to] + shareForX ==
            senderBalance + receiverBalance);