1) Right click on game name in the steam library
2) Select "Explore files"
3) Open SteamLibrary\steamapps\common\Gothic\system\gothic.ini and change zStartupWindowed=0 to 1.

4) Set your native resolution in the same file by changing the following lines (you can find your desktop resolution by checking your Windows display settings):
zVidResFullscreenX=1920
zVidResFullscreenY=1080

5) This way, it will look like fullscreen but won't crash while minimizing.