Apperently MP and Singelplayer Saves using the same slots... I lost 3 days of progress in my singel Player Session because i wantet to play a game with my brother from the start... All my autosaves and Quicksaves wher overwritten in that game session.. Thats the worst...

You should never, ever, ever, rely solely on auto/quick saves for your games, ESPECIALLY content-heavy RPGs. That's just asking for something to happen to them.

Don't get me wrong, it's okay to use them, they're there for a reason. But you should periodically be making an actual save.

Amen--don't know why people play like that. Aside from autosaves, which I allow, I save every game manually, and 95% of them I rename into something recognizable to me so that I can look at the name and know exactly where the game was saved. Trying to play without manually saving is, imo, just asking for problems just as described here. The save-game function is very flexible and powerful, but not if you don't use it, eh?...;)

Sorry for your loss of progress but always make manual saves at key points in your gameplay. I also recommend you regularly back up your saves for good measure.

I make a habit of making 1 acutal save every time I go to log off the game. That prevents any overlaps with saving from other saves.