For vanilla (unmodded) installations, the intended way to is through the launcher before the game boots. Here is the step-by-step process:
Many players prefer the immersion of German voices with English text. If the in-game settings don't allow this split, you can manually swap files: Navigate to your game installation folder (e.g., Silent Hunter 5/Data/LngGameData/Voices/German folder found inside that German directory. Go back to your main Silent Hunter 5 directory and paste it, choosing to all files when prompted. silent hunter 5 change language