Fix praguemorning.cz 502 Error

My news site praguemorning.cz has suddenly started returning a 502 Bad Gateway on every page. I have not touched the server, code, or Cloudflare settings before the outage, nor have I attempted any fixes yet... (Budget: €8 - €30 EUR, Jobs: Apache, Cloudflare, Linux, Network Security, PHP, Troubleshooting, VPS, Web Development, Web Hosting, Web Security)