Now don't get me wrong, the game is amazing and great with friends, but the online functionality is broken. If you check the community forums, you can see that this has been an issue for a while now. Servers constantly working then breaking, the devs seem to not care at all. Oddly enough, gog seems to be aware about this since I have emailed them a while ago, but nothing has really come from this.
For single player you are able to resume from where you last left off, but this feature is not present for coop. It makes it a dealbreaker for me as my friend and I cannot play for long sessions, rendering it impossible to finish this game. There were talks from the dev that this "resume" feature would be implemented, but that was years ago. Avoid if you plan to play this with friends but cannot play for long sessions
