That's strange.
I know that certain types of games are blocked in Germany.
But I can still buy both big and small games with tits in them.
Must be a new thing...
Sorry for the late reply.
In Germany the game either needs an age rating via the USK (PEGI is not valid in Germany) or an age rating that is issued by Valve through its own self-rating process.
The self rating process should be available for you under the following link: https://partner.steamgames.com/healthcheck/missingratingforgermany/