Squares on textures

if nvidia you can enable upscaling to a higher resolution with compression to a smaller.
or use a different type of antialiasing if the game supports it such as msaa
or use some program such as enb or ReShade do soap after the main rendering
or look for Disable disappearance of trees if there is such (I do not remember)

it is not a bug this trick only in the screenshots at a strange distance is dissolved.

you have a problem with shadows. most likely the anti-aliasing on your graphics card isn't right

Helpful, thank you)

It's originally designed to see the character even if the camera is behind the object. (It's just that the filtering in your case isn't smoothed.

Maybe you should try increasing the drawing distance

The interesting thing is that this problem is with nvidia graphics cards, and it's not only in The Witcher 3 but also in other games, for example in Horizon and several new ones.