2FA must be activated before the withdrawal. This is an additional way to secure your investments. You can activate 2FA in your personal account. You have to go to settings -> 2FA. Then you need to download the Google Authenticator app, if you don`t have it. Next you have to scan your QR code. After that the app will show you the confirmation code which you need to enter in your personal account. Then 2FA will be active.
You cannot turn off 2FA on your own. It`s an important step for the security of your investments so you`ll be able to turn off it only with the help of technical support.