so i have a little Problem with Cloudflare and my NGINX Server. Everytime i disable Under Attack Mode it gets the Error 520 but only if in NGINX fast_cgi_cache is enabled.
So my question how can i use fast_cgi_cache with Cloudflare without the Under Attack Mode `?
Are you saying that with Under Attack mode on, your site works? It sounds to me like your site is under attack and goes down trying to answer all the requests.
Under Attack has nothing to do with the 520 on your server, other than stopping bad traffic. It could be that your host’s fast_cgi_cache process is failing and you’ll need their assistance to fix this.