Diagnose Cloudflare TLS and SEO Issues

I need your help investigating and optimizing my website, meister-job.de. My website runs on a dedicated server with Next.js, HAProxy, PostgreSQL, Redis, and Cloudflare (Free plan). Current Problems I experience occasional, unusual connection and TLS errors, including Cloudflare errors 522 and 525... (Budget: €8 - €30 EUR, Jobs: Cloudflare, Linux, Next.js, Nginx, PostgreSQL, SEO, System Admin, Ubuntu)