if you own a physical german CD of the game, then you can simply overwrite the data in the gog gamefolder with all the data of the cd-rom. Afterwards you may reconfigure the setup but that's all it takes to switch the game manually to german language with all the german voiceovers and text.

I've had this problem recently, and I didn't really know why because I'd never had that before in all those years.
Now I've FINALLY found out what was the problem.

If you install the game from the original German CD under DOSBox, it somehow doesn't copy ALL the neccessary files to the hard drive.
In order to make it COMPLETELY German, here's what you need to do:

In the \DATA\ subfolder, you'll see that there are the following .RES files:
RES.000
RES.001
RES.003
RES.005
RES.006
RES.008

In order for you to have full German voice acting (not the occasional English voices), you'll also have to copy the
RES.007
from the CD to the DATA folder on your hard drive!

Then everything's as it should be.


(Basically, I could upload the German files, so you all can turn your English version into the German one.
IF... that's allowed. ;) )

Well, you could upload them somewhere else and inform us ;)