Thanks, I've got your PM with your website info.
Far as I can see in your dashboard stats, you have several issues with your server configuration. Most notable issue is the 7200 seconds of max_execution_time which should be at most 120 seconds. When you increase the max_execution_time you will always have several issues related to bad request handling, in this case, you are allowing request to take 2 hours to complete which I assume you did to allow 100MB image uploads.
The 100MB limit for image uploads is also a don't, at least with 7200 s. That should be almost 30MB. The 7200 s + 100MB allows an easy ddos attack in your website, something that you should avoid.
Secondly, I don't have access to all your php.ini settings but I'm sure that you edited several other things without knowing the impact of some changes. Maybe your keep alive is also huge or your timeouts are also wrong. Problem of this is that after someone leaves your website your keep that sub-process alive for an unnecessary period of time.
Finally, I've noticed that you are hosting a lot of content but all in the same single server. You are putting a lot of stress in one single machine. Doesn't matters how much RAM or CPU you have, your network adapter is limited, your disk I/O is limited, etc. Try to fix your server settings and then check this guide I just did:
https://chevereto.com/docs/going-big
Hope you can send me FTP access to perform some test in your server, maybe there are some other issues.
Cheers.
