Graphic artefacts cause huge lags

For several weeks now I had a recurring problem with graphic artefacts in ground battles which appear as multicoloured raindrops appearing randomly during battles (see screenshots). Their number increases in 5-seconds time until it distords the image until it freezes. The game eventually disappears (image goes back to desktop) and reappears seconds later, with graphics quality altered. Sometimes it even crashes. And that can happen several times in one single battle, which is, you’d understand, far from ideal gameplaywise.
My particle density in graphics settings is at the lowest and overall graphics settings are at a medium, I don’t overload my graphics card and I download Nvidia driver updates as soon as they are released.

Thank you in advance for looking into and dealing with this issue.

I’ll add a couple more images and details here:
I never had such problems with graphics before, and that was happening before I added the custom gun sight you can see. These artefacts appear whenever there is some kind of particles (rain, mist, for, smoke, sandstorm, snow, etc…). Again, before this problem started in the last two major updates, I had no problems with the particles and effects listed above, and I haven’t changed my settings, sitting at average and not overloading the graphics card in a long time.
Plus, lately, glitches started to appear with water: is transforms into a blicking grey grid and eventually disappears completely.
All those lags, when severe, even cause a loss of signal from the graphics card (screen goes black and searches for source), which is, again, very far from ideal when in-game.

Update No.3: the lags and artefacts’ appearance have increased in intensity and in the number of occurrences. They persist even if I lower my graphics settings. Something with incompatibility of textures and drivers, despite them being up to date…

Update No.4: I’m just desperate. The artefacts appear more and more often, even at low graphics settings…and the lags they cause are ever so more severe, up to 20 seconds of freeze…it cost me several games, where I was destroyed because I couldn’t do anything while my game froze…
If it continues to glitch that much, I might aswell stop playing.
By the way, War Thunder is the ONLY game that I am experiencing any lags with. Other run without problems, even at high graphics settings.