Unless you know the owner of a privately owned 150, you will need to be fully checked out in the 150 by a flight instructor, who will judge how much/little training you need to be able to rent that type from the club/school, also many reputable school's will make sure you are fully proficient before allowing you to take one of their aircraft on a land away, particularly overseas.
Like I said unless you know a private owner who is willing to risk lending you his aircraft at this point with your low experience and not knowing really what your doing to go to Germany, chances are (unless your really good at bluffing the school!) you will be going nowhere.
Oh and prepare for a lot of sarcastic replies on this thread.
