Website error


Yesterday carry out the following test:
on the website, install a module with critical errors. It was a deliberate action.
As expected, the site gave an error, the unexpected thing was the loss of access completely

in the browser:

Hmm. We’re having trouble finding that site.

We can’t connect to the server at

If that address is correct, here are three other things you can try:

Try again later.
Check your network connection.
If you are connected but behind a firewall, check that Firefox has permission to access the Web.

in the explorer (ubunto 20.04 lts)
![Screenshot from 2021-10-27 10-45-20|655x182](upload://nokvwLJE5r7yTeCubX0aWk23nKQ.png)

My questions:

How to recover a site? where is the backup/restore tool?
How to access the Database, <yoursite> /dbadm.php
Why is access to WebDAV lost?

Best regards