GPU overheating? / texture rendering issue

To begin with: I'm playing with an eightcore AMD CPU and a MSI 1070 GPU. I have a few mods installed, like bigger scan radius, some additional hairstyles and the Mod Manager of course. 

I recently had some PC shutdowns that occured ALWAYS in the cutscenes either directly before or after the very first bossfight. One time, I just heard a humming while I got a bluescreen, the other time I got a bluescreen while I still heard the ingame sounds, most times of those crashes were a sudden completely shutdown. MSI Afterburner showed a GPU temperature around 50°C and higher, so I guessed heat was the problem.
Well, I knew I had a really bad CPU cooler, so I got a new one, also I added another front vent. Had to be done anyway.
That did it at first, since then I had no more crashes. Guess my system got too hot and went down. (My bad.) However, some textures don't load properly now even when I'm on the highest settings. They don't even to render at all. (Screenshot attached) That doesn't affect all textures, most NPCs are depicted with the ultra-settings, as well as most of the ground or even some walls. Others look like on the attached screenshot. 
By Afterburner the temperatures of the GPU while playing are around 50°C while by Core Temp the CPU has around 40°C. That makes me think my GPU got still too much dust and tends to overheat.
Is it possible that heat decreases the power of the GPU or that the heat already damaged my GPU?

And how can this texture problem be solved? 

I haven't yet reinstalled the game, but I have deinstalled all the mods. The PC shutdown is hardware related I think, and the game worked perfectly for half a day after the crashes were solved, before the texture problem occured. 

Edit: here's the link to the dxdiag-file: https://hastebin.com/jarexajoyi.tex