What I'm looking for is the music from the waterfalls near Silden, and I want to get the one from the G3 folder since the ones I found were different...
Do you hear something about the NicoDE's Gothic 3 - PAK Viewer tool? You can extract all Gothic 3 music (include rejected variants) from the Music.pak and Music.p00 packages. I recommend to unpack contents of the fragments folder only and listen it with a player supporting the Vorbis Audio files (.ogg).