i managed to do it with the PAL version, may be different if you have the NTSC version.
for me this removed about 400 or 500mb and made the game just 4.02gb:
in the \Res\Sounds folder you can delete any files named *ge.xwb
these are german sound files, you obviously won't need these if you are english speaking (or vice versa, you could delete *en.xwb to get rid of the english if german is your first language)
this way you don't lose anything at all, unlike the other method posted on here which involved replacing sound files with dummy files and thus losing the speech and requiring subtitles to play
________
American