I, unfortunately, don't know how to help with the problem - but I just wanted to anecdotally mention that my GOG-purchased Risen 1 was very, very stable. I often even left it running overnight many times (paused) between play sessions. I don't think it's the game itself that's crash-prone.
Common advice is - maybe some anti-virus program is to blame. Might be something to check into..
Hope you find the "cure' - it's a really fun game and a nice little open world.