I recently bought the game

Sry, accidentally clicked on "post".
So...I bought the game recently and am experiencing crashes, when entering a new area. I searched online and found out, that the sound files may cause this, but the offered solutions did not work.

I am also experiencing AI Bugs.
For example, in the first mission "Surf up" I just can walk past the guard and enter the house and nobody will notice me (without sneaking). I can also just kill someone in front of a cop and he will not do anything. I checked if AI was just disabled, but this is not the case.

Have you tried reinstalling the game? Those problems really sound like some sort of file corruption.

Tried it multiple times.

Can you see "Unofficial Patch 9.5" on the right if you go Options and then Gameplay tab?

Also try the following: open the Unofficial_Patch/maps/graphs subfolder and delete the sm_beachhouse_1.ain file. The game will rebuild it and with some luck, the AI at the beachhouse should be fine again...

It is not only the AI of that one level. All of the AI behaves wrong.
I just got a refund now, so that I can buy something with the money while the sale is still on.
Still thanks for your help!

Sorry for asking, but HOW can you check if the AI is disabled??? Please tell me?

A typical symtom is NPCs just standing in one place and not doing what they are supposed to do. Then after you remove the ain file when restarting the map you get the info "AI node rebuilding" shown shortly on the screen.