WordPress Hacked

Our problems:
the homepage looks original, but:
– wp-admin – does not load – redirects us to the home page
– all links from the menu link us to the home page

We can’t get into WP-Admin – and we can’t solve it

Our provider wrote to us after the consultation:
Your site has been hacked. The attacker blocked your access to the admin via .htaccess, when we disabled .htaccess, it allowed us to access the admin page, but it will then generate it again on ftp. It will be necessary to check the entire site with a programmer, including scripts, to clean it, and I also recommend that you scan your device for any malware or similar problems.

Can this be fixed somehow?
Thanks for any help

The page I need help with: [log in to see the link]