The requested page "/" could not be found and I can't see admin menu. Help Please.

Hello, i need your help please.

From night to day i lost all the content of my website and the message is:

The requested page "/" could not be found.

I also cannot see the admin menu, just the home icon, but nothing works, neither cron, flush caches, etc.

I already tried .htaccess with a back up, also try with a backup data base and nothing works.

Any ideas what could happen and how to fix it. Thank you.