I play on a laptop and have two graphics cards, one integrated and one discrete. And when I run games NOT through gog, then the discrete video card works and everything is ok. But when I run the witcher or cyberpunk in gog, then for some reason the integrated video card starts working, and I have small fps.

This problem appeared a couple of days ago, especially after the recent cyberpunk update (although I don't think this is related, because the witcher also started to work incorrectly)

Maybe someone faced this? And yes, I already changed the settings in the nvidia control panel and windows panel.

Try to change gog settings if gog specifically has the issue.

Unfortunately I didn't find any settings in gog, where I can change graphic card or something similar

Can you select a graphics card in the game's settings?
Can you disable the integrated graphics card in Windows Device Manager?

Neither in cyberpunk nor in the witcher you can not choose a video card.
Also, I can't turn off the integrated video card, because it uses for the display.

The support article Laptops equipped with two graphics devices suggests that if global settings don't work, you should create a custom profile for the game.
If you haven't already done so, create custom profiles for the games and GOG Galaxy as well. Note that some games have a launcher executable which differs from the game itself. GOG Galaxy is also spread across multiple executables, in both C:\Program Files (x86)\GOG Galaxy and C:\ProgramData\GOG.com\Galaxy.

You can also try updating your graphics drivers and disabling the overlay in GOG Galaxy, just to see if that makes a difference.

Other than that, I can only suggest that you open a new support ticket, if you haven't already done so. Be warned it may take weeks to get a reply.

Sounds like one of them Intel-Integrated+NVIDIA-Dedicated lappies. Go into your NVIDIA Control Panel and make sure that the setting for your game is set for the NVIDIA GPU. On my lappie it's quite common that the auto-tuning setting will choose the integrated chip over the actual GPU, so I often have to do a manual adjustment.

Don't forget to right click the game executable and go into Compatibility settings to turn off full screen optimization.

This will give you a few extra frames in a laptop and UMPC. Windows tends to fiddle with gaming in small computers and the screen will look blurry because the OS is using "optimization". More like making a mess as usual. Also, yes, you would have to manually change this setting with every game you have as well as make certain what is changed actually launches the game. Not the game launcher.

I found the problem. It was Microsoft Defender(antivirus that there is in windows 10). So I just created an exception in this antivirus for the folder, where I have my games from GOG.

Please explain what method was used. Was Windows Defender blocking your option to define the correct GPU?

Odd. I've never had any problems like that with Defender.