top right corner tabs are gone (_ square and x)

[stevef]

I'm a new Linux user and my native language is not English, so I apologize for any technical or language mistakes

Hope you are not put off using Linux.  If you are using a new system in a second language there's no need to apologise.
Please ask for clarification if you don't understand.

As for trying to open the manager window, I can't do it, when searching in the search bar and clicking to open nothing happens

If 'Window Manager' appears in the results window but nothing happens when you click on it then it suggests something else is wrong.

There are other ways of opening 'Window Manager' - for example
If you can open a terminal (press Ctrl, Alt and T together) then typing this command followed by enter should do it.

Code:

xfwm4-settings

If that works, it will open the 'Window Manager' and you can check under the 'Button Layout' section on the right hand side.
If the missing buttons are in the 'Hidden' section click and drag them onto the 'Active' pictogram.

But, if basic things like buttons being where they should be and starting applications like Window Manager with a click are not working properly, it may be quicker to step back.
Do you have System Restore Utility (Timeshift) and Backups (dejadup) snapshots from before the problems started ?
Would you be prepared to wipe the system and start again ?