All apps are damaged or incomplete - Appear as Question marks

Hello,

Could you please help me solve this issue?

Suddenly after starting up my laptop, all applications appear as question marks. When I try to launch any application I get a message that it can't be opened because it's damaged or incomplete.

I tried to:

• to start my laptop in safe mode but I have the same issue
• to create a new administrator account but I am unable to open system preferences

Could you please advice as to what else I could do to try to repair it?

Thank you very much in advance!