thanks for the reply!
I got in contact with the GOG Support, right now I am two hours into playing without any problems.
Hope this is really the solution.^^
In case someone other the same issue, here the step the support told me (Can’t put all the liunks here since I am a new user):
Please add Galaxy folders:
C:\Program Files (x86)\GOG Galaxy
to your security software exceptions list. If the game is installed outside of GALAXY folder, then please add game’s installation folder to security software exceptions list as well. Once above is done, please select the game in GOG GALAXY , click on the customize button (to the right of Play)-> Manage Installation → Verify/Repair.
Reinstall the June 2010 DirectX runtime package. You can find the archive file containing the 2010 package installation files here:
Download DirectX End-User Runtimes (June 2010) from Official Microsoft Download Center
You will have to extract the files into some folder, then open that folder and launch the DXSETUP.exe file in order to proceed with the installation.
After that please download and install DirectX Web Installer:
Please have in mind that this will only add DirectX 9.0c to available pool of DirectX libraries, and it will not overwrite your other versions. Some games are not able to utilize newer DirectX libraries, and they require DirectX 9.0c.
Please update your graphics device drivers
Please set a more standard refresh rate (60 Hz). To do this right-click an empty space on your desktop, select Display Settings > Advanced Display Settings > Monitor tab > change the Screen refresh rate to 60 Hertz.
Please navigate to the game installation folder:
If the game was installed via GALAXY, please select the game in GALAXY, click on Customize (to the right to the ‘play’ button) → Manage Installation → Show Folder
If the game was installed via offline installer, then you will have to manually navigate to the game installation folder, by default it’s: C:\GOG Games\game-title\
Once in there find game’s “Launch” shortcut, right-click on it, and select Properties. In properties window switch to Compatibility tab, and here enable “Disable full screen optimization”, as well as “Run as administrator”. Press Ok to apply settings. Right-click on the game’s “Launch” shortcut and select “Run as administrator”.