Hi,
your site run very smoothly on my machine. In my case I noticed that, if I had the editor mode on (if you have it on, you’ll find a tab with a little arrow on the bottom-right corner of the page, the page lagged a lot, Try different browsers, or incognito. Then log out from editor mode, clear your cache. No you should see the page without the editor arrow tab and your page should run smoothly. Have a look at this Disable the editor after it has been enabled
Hope it’ll helps!