For German undergraduate and graduate math classes, does the professor or assistant write the exercise sheets?
In the United States it is typical for the professor to write them. I am curious what the situation is like in Germany.
At my university in every class I had and heard of the assistant wrote the exercise sheets(and often the exam too). Many times the professor did not even fully know which tasks are on the current sheet. Of course this varies a bit, in later more advanced classes the professor is typically more involved in the exercises.
From my limited experience I can confirm that most of the time, assistants write the exercise sheets and exams (and often the professor has at least a look at the exam). What I want to add is that there is a lot of recycling going on: When it comes to lecture slides, I often notice that many professors just change the name and dates on last year's slides or use the previous lecturer's template.
This is in my experience also true for exercise sheets, at least when the professor is the same. Rather than writing new exercises every semester, assistants combine exercise questions from previous years and sometimes add an old exam question. So it might be the case that a professor has contributed to the exercise sheets when he started giving the lecture and after that, it's mostly assistants doing the work.