Websites always hacked

I deleted every database, and user,
changed every password,
updated every single plugin and theme
and did everything to protect the website.

The things you have mentioned are not enough to make a site secure. You next need to “harden WordPress”, and I do that by using BulletProof Security…
https://wordpress.org/plugins/bulletproof-security/

Then to add a firewall out in front of the site, I use NinjaFirewall…
https://wordpress.org/plugins/search.php?q=ninjafirewall

Along with those, I also use Wordfence Security for some of its features the others do not have…
https://wordpress.org/plugins/search.php?q=wordfence

Hi Ioscamos

With that many domains, managing their security can be challenging. Have you ever considered leveraging a security service provider like Sucuri? Especially if you’re continuously getting hacked, sounds like it might be time to get some professional help.

With an environment like this, there are multiple places to account for with issues. Here are two articles to assist:

https://blog.sucuri.net/2012/07/website-malware-removal-wordpress-tips-tricks.html

and

https://blog.sucuri.net/2012/11/website-malware-removal-ftp-tips-tricks.html

Hope these helps, let us know if you need more help.

Tony