I have been wondering for a long time whether I can react to films or something similar on TV live in the stream and whether that is somehow legally not good even if you still play the advertising completely in the stream?
You are not allowed to react to any TV programs / films unless you criticize and rate them, but then you are only allowed to show scenes that are relevant for the criticism, i.e. Not the entire film
Can I watch TV (Prosieben etc) in my live stream (Twitch).
Yes you may.
If you have the rights to do it. But I dare to doubt that very much.
So the answer is: NO, if you want to show LIVE programs.
Otherwise like CraftCreep said