The problem is in PS, I cannot use the full menu; a large part of the menu is darker, and I cannot click on anything

When the User Interface (UI) is mostly dark like in your screen shot, it probably indicates that it is waiting for input.  Just hitting escape might cancel out of that situation.  There might be a panel, or pop-up asking a question (waiting for input) that is off screen.  Try reducing the Photoshop window, if it will let you).  

Resetting Preferences as suggested by ​@AxelMatt should return the UI to its default state. 

Try to reset the preferences to the default settings. Manually removing the preferences files is the most complete method for restoring Photoshop to its default state.

This method ensures all preferences and any user presets which may be causing a problem are not loaded. Please follow the steps below:

1. Quit Photoshop.
2. Navigate to the preferences folder of Photoshop.
   MacOS: Users/[user name]/Library/Preferences/Adobe Photoshop [version] Settings
   Windows: Users/[user name]/AppData/Roaming/Adobe/Adobe Photoshop [version]/Adobe Photoshop [version] Settings
    
   Note: This folder is hidden by default. To access files in the hidden user Library folder see the appropriate links below.
   MacOS: How to access hidden user library files.
   Windows: Show hidden files and folders in Windows
    
3. Move the entire Adobe Photoshop [Version] Settings folder to a safe place on your drive for a back-up of your settings. Then delete this folder.
    
4. Open Photoshop.

Photoshop creates automatically the appropriate settings folder with the default values.

If this doesn’t help we need more informations about your system.

Which version of Photoshop do you use?

Which operating system (and version) do you have installed.

Is your system up-to-date? Do you have installed all recent updates and patches for the operating system and the device drivers, especially the graphic driver. Please make also sure that you have installed the Studio version and not the Game Ready version of your NVidia driver.

What has been changed on your system before the error occur?