I was wondering if anyone knew whether or not it was possible to configure the game to use the German audio while still having the English subtitles?
Yes, it is possible, but you cannot do this on-the-fly while playing the game.
1. You need first to put the "prince_translation.dat" file from the English "version" into the "ALL" folder of your German game data folder. You don't have to install the English version to get this file. You can find that identical file on the ScummVM site (the ScummVM team did the English translation for the game), under Game Addons here: https://www.scummvm.org/games/#addons-prince
2. Edit your prince.ini file in your German game data folder and add the following text to the end of the file:
description=The Prince and the Coward (w/translation/Windows/English)
Keep in mind, the "path" above should be set to the path of your German game data folder, so it could be different for your specific case.
Save the prince.ini file.
3. Create a copy of the "Launch Galador" shortcut and rename it to "Launch Galador En". You will use this shortcut to launch the game with English subtitles.
4. Finally edit the new shortcut ("Launch Galador En"), by right clicking on it and selecting "Properties".
Set the "Target" field to:
C:\Games\Galador\ScummVM\scummvm.exe -c "..\prince.ini" prince-en
Again note that the subpath "C:\Games\Galador" here also could differ on your case, based on where you installed the German game data.
Press Ok. And that's it.
Use this new shortcut to launch the game with German audio and English text (and UI).
Note, that this can also be done similarly for the Polish installation of the game (Polish audio, English text) but *not* for the Russian installation.
You won't be able to directly share saved games between the two versions of the game though. The all-German version and the German-English version will name their saved games differently. You can of course rename the saved games to match one of the two versions and they should be compatible.