I tried to play Noctropolis, but it isn't possible, because the game shows no text, neither in English, nor in German.... what could be the problem. I just see grey boxes.

I have the same problem. I have searched through the internet for a solution but nobody has commented that problem yet.

Try reading through this thread:

http://steamcommunity.com/app/377070/discussions/0/520518688943274819/

I'm having the same issue, and according to the dev in the Steam thread, it might be related to Win 8 drivers, since it seems only people on Win 8 have this problem. It can be fixed by activating windowed mode, but I really don't like not being able to play my games in fullscreen mode; windowed mode is immersion breaking to me. IMO, GOG shouldn't list this game as supported on Win 8, if it means lots of Win 8 users can only play it in windowed mode.