Tried everything, maybe I do something wrong.
Here is the file, if someone has the time and passion to take a look at it.
The big cylinder"thing" (first) has to be inside of the rectangle (second) by subtracting.
forum.skp (156.1 KB)
thanks a lot
EDIT: I made a new project, now the big cylinder has to be subtracted, not the small one, as in the screenshot. Same in the end but other did not fit and now the big one even doesn’t work.