Problems with Error 504

Hello, I’m having problems with error 504 on my website.

I already contacted my hosting, but they said that everything is normal and that it is a Cloudflare error. But I can’t find a solution, Cloudflare error 504 instructions, and it didn’t help me.

Hosting recommended me to disable Cloudflare, but I wouldn’t like that. What can be done?

My site:

I had to disable Cloudflare on my website. But here is another site on the same IP with the same issues: