Hey Tim,
thank you for the answer. It more or less did the trick.
I managed to disable the capability "edit questions from other users" but I can still copy them. So far so good...To make it really good it would be great if I could copy the question to my own course category. In my case the questions are stored in the course section category (e.g. Marketing). Copying a question from that bank is only permitted, if I save it to a bank of the same hierachy level (not to my course (e.g. Marketing class xy) although it is inside the section.
Any ideas for that problem?
Cheers
Tobias