It's a little difficult to explain, but at a high level, we're a single page app, which means when you click on an anchor, we request the JSON for the new page, render the html on the user browser, empty everything in #content, and inject it into #content. The overlay is a transition that makes this process a little smoother.
We use a templating engine called Benchpress to render templates on both server and client-side.
@pitaj vestacp has several nginx.conf. As I mentioned I edited "site-specific" config in /home/admin/conf/web where vestacp keeps configs for all hosts, inculding ssl and lets encrypt.
Maybe you mean global nginx.conf which is located in /etc/nginx ? I did no changes in it.