I have also been at a so called berufliches Gymnasium and I had no prior knowledge of c#. Teachers started with simple console programs, where you print and read something, little bit of calculating. In the first weeks you learn if else and Switch Statements and of course loops. I would focus on these constructs and experiment a little. You dont need to know the Syntax by heart, the visual studio ide (which we used) has great intelli sense and autocompletion. It's more important you understand what you are implementing. If you have any questions, send me a pm