wp-admin login page error

Hello,

I posted earlier here: https://www.ads-software.com/support/topic/wp-admin-login-page-error/#post-9395039

But I could not get my issue solved: When I try to log in to wordpress dashboard, I get this error and deleting/deactivating plugins/themes via ftp does nothing, the plugins stay active no matter what I do and the login error persists. I am willing to give ftp credentials, if someone thinks he knows how to fix this.

I have struggled with this for a week now, looking forward to your answers WP community,

Kind regards,

Stefan Dyankov

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