Too many to list. DLR - Germany's NASA - is a key player in Europe's space industry, so it draws all kinds of space companies to its neighbourhood.
EDIT: those two links might give you a quick overview:
- https://spaceindividuals.com/space-companies
- https://spaceindividuals.com/space-jobs?country=Germany (over 50% of all listed, but not surprising, since the site's owner is in Germany as well)
Right now, I'm trying to map the industry myself.
I wish I knew more about this subject.