mepe_ruse: Is the game still Auto saving? check your save files for either an "Autosave" or a "Checkpoint"
Have you tried hitting F5 while playing & seeing if you can Quicksave?
If you are near any Enemies or are in combat you cannot save so make sure you are in a safe place & the combat music isn't playing & then try saving your game.
Have you tried reinstalling the game?
before you reinstall the game make a backup of your gamesaves file & take note of what version of the game you are playing & what DLC you have installed, then patch the reinstalled game to the correct patch & DLC content.
It is also a good idea to contact the GoG support team & explain your problem to them
I have done all of your suggestions. Nothing happens. There is noch "letter Icon" when hitting F5 and
there is no new savegame regardless what I do. Even after successing a new Quest there is no new Checkpoint.
And yes, I contacted the GOG-Support but don't hope to get answer in a few days. Maybe 1-2 Weeks....
Ist very strange.
I let GOG Galaxy check the game and everything is fine and the Game itself is rockstable now, no Crash in the last 6 days !