Tokenomics and is buying/selling in crypto the same as transfer?

Smart Contracts
1

good morning.

yes, my main question is about tokenomics- however, one thing confuse me profusely!
Is buying a token from DEX/CEX the same as transfer? and if so or not so, does buying tokens from DEX/CEX invoke the transfer function?

anyways, if any one is able to provide some clarity with the question above I will appreciate it with much gratitude.

okay, so the main question of this post:
I am trying to add tokenomics to my token (a 10% tax for buying, 20% tax for selling). I have already added taxing to my transfer function (I will paste the code at the end of this post), however, I am not sure how to add this to buying and selling of my token. (Like when someone buys from pancakeswap)
I've scanned safemoon's code on their GitHub and found no buying/selling function(s) that was using tokenomics- however, I've noticed transfer functions (which has me confused as to what actually happens 'under-the-hood' when tokens are bought. hint, my question above).

//Adding Tax To Transfer(s)
    function transfer(address recipient, uint256 amount) public override returns(bool){
        
        //conditions
        require(recipient != bankerContract, "Cannot Send To Bank");
        require(recipient != burnerContract, "Cannot Send To Burner");
        
        
        address sender = msg.sender;

        //Checking if no tax is applied
        if (excludedFromTax[msg.sender] == true) {
            _transfer(sender, recipient, amount);
        }
        else{
            uint256 bankAmount = amount.mul(taxFee) / 100;

            //Sending to bank (tax)
            _transfer(_msgSender(), bankerContract, bankAmount);
            //Sending To Address
            _transfer(_msgSender(), recipient, amount.sub(bankAmount));

        }
        return true;
    }

the token is ERC20, and openzeppelin's library is installed. I am using truffle for developing this token and my text editor is VSC.

I did notice one method- or I think it's a hook of sorts... called _beforetokentransfer. It is an empty function, but do I create the taxing inside this function?
I think there is also an _aftertokentransfer which- I'm guessing- is where I would implement burn functionality if I had something like 'auto burn after every X amount of coins bought'

2

you can put your taxfee code under it, but what's your amount.mul(taxfee) planning to achieve?