Malware infection? HELP

Hi,
I just run into some kind of malware that doesn't allow most of the .exe files in my laptop to run.
My system: Windows 10 on an HP laptop with Intel i7

Basically I started uncompressing a .rar file using the 7-zip software (which I had used in other occasions without any problems) As soon as I try to uncompress the rar file, most other executable icons turn into the 7-zip software icon and most other executable (but not all) don't run. If I click on them the 7-zip software executes.
Even system software such as Task Manager can't run. If I try to install a new software, immediately the 7-zip fie interface appears after clicking on the .exe file
My Avast ANtivirus software doesn't detect it (haven't yet tried to restar the laptop so that Avast can scan the boot sectors, for fear to not being able to access my data at all after restart)

Not all programs seem to be affected though. For example notepad.exe or Adobe Acrobat Reader, the Calculator and some others aren't.
But basically it has taken control of my laptop
What kind of virus is this? What can I do to remove it safely?
Best regards

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