Okay, i now can say for sure that it was caused by my screen, the problem occured not even once last week.
To summon up:
I had a black screen in the game coming, but game runned netherless (sound work normaly). Problem was: My Monitor (blackhawk by iiyama) uses something called "overdrive ...
thank u for your advice, temperature and stability were just fine.
But i think i figured it out...
I was altering every graphic option i was able to found, and started even to alter the settings on my monitor. I checked them before and never thought that there could be the spurce of the problem ...
I have a very strange problem: When i play the game, my screen starts to flicker, and ultimately turns black. The game although goes on (sound is smooth, can hear my footsteps as nothing is wrong) I can get a normal screen again by turning my monitor OFF and ON, but the Problem occurs ...