On my laptop do I no longer see the files that I have on the screen as a document / file?

I connected the laptop to a monitor and it worked for Prime for a long time, but since recently I see nothing more than a blank screen with the toolbar. How can I have things displayed again permanently

Do you have the laptop open? Can you see everything there?

This is some system error.
You would have to start looking for an exact error now.

You don't see any symbols on the laptop or what?

Go to the file explorer, top left with quick access to the desktop and see if everything is still visible.

If so:

Right click anywhere on the Desktop → View → Show Desktop Icons

If not, you deleted or moved the files. Look in the trash