Thanks for the help, pacov. My friend and I played another two games yesterday evening. One game against each other and one against the AI again.
In the first game I received favor points for finishing the game (all the rewards) and the achievements. In the second game I didn't get any favor points at all again. The weird thing is that my friend's achievements are saved and mine aren't (even the easy ones like "win a game").
When I started with the game a few months ago (and it was a pain to get into a game
) I liked to play against other players, it was more of a challenge. But because my friends internet connection has problems with this game when playing with more than 4 players and on larger maps even with 4 players only, we have to stick with the AI. So last time we played against 4 nightmare AIs, but it's still not a real challenge. 