Hi,
I recently checked your site and can see as you described: First content, products header and last slider revolution.
It’s a common behavior of any website that has the JS slider like this, because when the site loads, the browser will load the HTML first, then CSS and JS last, the Revolution slider is completely built with JS.
Thus I have a few suggestions below:
– Use the Cache plugin as well as compress js option to compress the JS file and improve it’s load time.
– Enable the Page Loading effect in the Customizer > General > Page Loading : http://prntscr.com/ogs5xm
Thank you