I am on a private tracker but not German content is uploaded. Anybody that has a tip can pm me!
One click hosters are pretty popular in Germany, so you will find lots of German stuff hosted one one of these. The most popular ones right now are rapidgator and ddownload. You will need special websites and forums for finding the links, though.
Everything which is aired on the public channels lands in the mediathek and you can legally download it for a while. Here is a handy search tool:
Usenet is the secret for German stuff. I have a German beginners guide: https://github.com/PCJones/usenet-guide