Unstake

unstake.sol

pragma solidity 0.8.4;

function unstake(uint256 amount) public {
        require(
            isStaking[msg.sender] = true &&
            stakingBalance[msg.sender] >= amount, 
            "Nothing to unstake"
        );
        uint256 yieldTransfer = calculateYieldTotal(msg.sender);
        startTime[msg.sender] = block.timestamp; // bug fix
        uint256 balanceTransfer = amount;
        amount = 0;
        stakingBalance[msg.sender] -= balanceTransfer;
        daiToken.transfer(msg.sender, balanceTransfer);
        pmknBalance[msg.sender] += yieldTransfer;
        if(stakingBalance[msg.sender] == 0){
            isStaking[msg.sender] = false;
        }
        emit Unstake(msg.sender, amount);
    }