Cache plugins make my site slower.

Trying to make my site faster I tried several methods and all was a hassle, because whenever I succeeded to improve something it get the something happens.

So, I tried plugins like W3 Total Cache, Autoptimize, WP Super Cache and WP Fastest Cache, but each one of them made my site slower and gave me error on pagespeed(Timeout while fetching the main resource. Ensure that the page loads in a browser and try again.) and on gtmetrix(Analysis Error. An error occurred fetching the page: read timeout).

The site is: https://www.dizart.ro
Is there a problem with the server, or what’s happening?

I am very grateful to each one who tries to help me to figure this out.
Thanks a lot!
Best regards!