Win10, CPU:E3 1230, Memery:8GB, Displaycard:RX 580 4G;
Texture was wrong in the city Novigrad.

What do you mean by wrong texture? Do you get flickering? Misplaced textures? Missing textures? Provide more details, so someone can help you resolve this problem. :)

I did upload a screen shot but cant see. icant post a link yet.like texture at wrong place.

What graphics card are you using? Driver version could also be helpful. I you don't encounter similar issues in other games, it's most likely a driver issue. You might try a different one.

I am fix it myself.
I doubt some game files was broken. I did use [verify/repair] with GOG Galaxy ,but always it show me "Installation failed: disk access problem" .
So, I download offline backup game installers [11 files total ] with web brower and reinstall again, then the pictures are right now.
Can't stop playing the game.
Thank you anyway.

Yep looks like many gog galaxy members has that same error or other similar errors when they try to use gog galaxy to DL witcher 3, I got it to with gog galaxy when I recently moved to a new PC, still not fixed. I had to use backup offline downloads to play the game. I am surprised CD projekt red has not fixed this issue yet... I know witcher 3 support is over but still... this game support feels more "abandoned" than older games here on gog...