How to delete AAAA records? I can't get SSL sertificate in hosting panel of my hoster for subdomain because AAAA

Cloudflare already have a certificate in place for your subdomain:

Your Origin server is reporting a 502 error, which is what is the most likely reason the certificate cannot be issued, and you should direct your initial attention to clearing that 502 error.

The 502 error is caused by a problem connecting to an upstream server - meaning your server is trying to initiate a process and this fails to work as expected or times out. In most cases of 502 errors, back-end servers are not communicating correctly. When this happens, you will see color page with Cloudflare branding and the Error 502 Bad Gateway . Review this Community Tip for fixing 502 or 504 gateway errors.