All resources serve slowly, so small .css files for example take a very long time to return.
This likely all revolves around poorly configured Apache + PHP (Opcache or APC, depending on PHP version) + MariaDB/MySQL (whichever is running).
W3TC usually slows sites to a crawl. You can prove this to yourself by running ab (ApaceBench) against your site with W3TC active + inactive. Try ZenCache instead.
Attempting to effect speed of this site using a CDN will likely be futile. Focus on TTFB first.
I would try to disable the plugins one by one and see if any one of them is causing the trouble.
If they all add to the slow down, then look for replacements or simply for go that functionality if it is just a “nice to have”
I would also consider swapping W3 Total cache for some other caching plugin. I know from experience that W3 Total cache actually slows some sites down.
I would recommend ZenCache as it is one that I use on all my WordPress sites:
If you’re using cloudflare, then all bets are off TBH! You’ve just added an extra level of redirection to your site, and while it may deliver static content faster, it cannot improve the TTFB as it has to talk to your original site and act as a proxy server. It doesn’t have it’s own personal high speed internet, it’s having to use the same one as us.
The only way it could conceivably help is if your server is a very long way away from your target audience.
Ignoring the hate campaign against W3TC - which is just as good as any other WP cacher when correctly configured ( ignoring the current annoying nag screen ) - a WP / Woo site on a VPS sized to 12GB memory will function well, and only a poorly configured server ( or an appalling theme!!! ) will cause this poor level of performance. Database needs memory and PHP needs compute power to perform well.
I guarantee I can improve this for you! Drop me a line if interested. Worst case, I’ll recommend an alternate provider (:
Note: I see the site is in Germany, audience in India (?) and your helpdesk in the Vatican! Testing the site from the locality of your target audience is always a good idea.
Edit: I see you’re running on nginx and SSL. Both of these can be better configured!