From what I can tell, the keys on the bottom row of a German Macbook Pro are as follows. A picture of yours may help to clarify:
Fn - CTRL - ALT/Option - CMD - Space - CMD - ALT/Option
PS the alt key is also know as an option key on macs.
Also it looks as though the @ symbol is on the key next to the Return key
From what I can tell, the keys on the bottom row of a German Macbook Pro are as follows. A picture of yours may help to clarify:
Fn - CTRL - ALT/Option - CMD - Space - CMD - ALT/Option
PS the alt key is also know as an option key on macs.
Also it looks as though the @ symbol is on the key next to the Return key