Could you please fill out the questionnaire, so the mod is no longer hidden in Germany? https://partner.steamgames.com/doc/gettingstarted/contentsurvey/germany

Hello, If you have a bug(s) to report for Half-Life: C.A.G.E.D., please post them here. Please provide as much relevant detail as possible including play difficulty level. Links to screenshots where relevant are also helpful. Thank you for taking the time to report your issues....

I dont know what should i do....

At least it's one of the best.

I've read somewhere, you was supposed to get an Item through the achievement, i think?