unknown error

Hi, I can’t exactly locate the error. Wp runs on Apache PHP-FPM and MariaDB. It manifests as follows. Some security headers are not working. / System cron – ERROR Detail : 409 Reponse : Conflict : Script already running or ERROR
Detail : 408 Reponse : HTTP/1.0 408 Request Time-out Content-Type: text/html
408 Request Time-out Your browser didn’t send a complete request in time. / Slow backend, extremly / Recently even on some pages in the background Error 503, service is not available.

Server log: Rejected, too many connections from this host. / client denied by server configuration
That’s all about it ?? There’s already so much that maybe it’s obvious to someone.