I cannot withdraw using Sofortüberweisung?
As Sofortüberweisung can only be used for the deposit transactions only - you will not be able to withdraw your winnings to it.
In this scenario where your chosen deposit method isn't configured for cashouts, you need to select another method, preferably one supporting both deposits and withdrawals, make the minimum deposit to unlock that method's cashout facilities, then the full amounts can be withdrawn therefrom.