Set up Twitch stream via Fritzbox?

We have recently had a Fritbox 6660, it runs perfectly, but it may be that I have to change something in the settings so that I can e.g. Can you stream a game on Twitch? When I start a stream, only the pause screen is displayed on Twitch. Does anyone know more?

This has nothing to do with your router

Check your webcaster settings (KBS / s Streamkey etc, resolution, FPS).

Okay, thank you for the quick answer