Games crashing + Black Screen

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Hey Guys,

 

I recently have the Problem that almost every Game is crashing and I'm stumped. I have no Idea what the Problem is.
So starting up a Game is no Problem and in most cases I can Play the Game for atleast 20-30 minutes, but after that Games crash or I get a Black Screen for a sec and the Game Closes itself. (PC is fine, doesn't crash)

I think, it's the Graphic Card but I don't know for sure. (Can it have something to do with Directx12?)

 

For Example I played WoW without Problems not too long ago, and suddenly I had those Black Screens, Game froze…After that I changed the Directx Version to 11 and it seems to be doing fine now.
Would like to know your Opinions on this…

Here are my Specs:

CPU	1 x INTEL® Core™ i7-5820K Six-Core 3.30 GHz 15MB
RAM	1 x 32GB DDR4/2666MHz Quad Channel Memory
GPU	1 x MSI GeForce RTX 2070 GAMING Z 8G 8 GB
Motherboard	1 x ASRock X99 Extreme 4
Powersup	1 x 700W be quiet! Pure Power L8 700W 80+ Bronze