Well, the game crashes for no reasons from time to time, and if you have no luck the inventory is totally fucked up (there are no item thumbnails). I've seen these bugs countless times on few computers, so they DO exist
The arena was supposed to have battles in it, despite those 3 guys. You can figure it out of what NPCs say in dialogue. There are also a few empty, pointless caves (I actually regret that there was nothin in there).
PS. Despite everything that makes Gothic hard to play, this game still is the best, I beat it 4 times and it still inspires me in terms of atmosphere. I love the music, and I can play a few tracks on guitar. And I quote texts from this game a lot with my friends. Cheers