Hey,
yes deleting the config files etc. worked a bit. It at least let me open the editor, all of my Blueprints worked except the gametype was broken. when i just clicked on it, the editor crashed. So i took it out of the Folder, reset to default gamemode, and brought it back in. After fixing an event dispatcher, i could use it again from there.
So thankfully no dataloss! 
The crash error seemed to occur because the Editor wants to load my messed up Gamemode.
Thanks & Greetings