fullscreen video tubular background

Hi, I've already read a similar post about background video but there's no solution for my trouble.
Can you help me with recognizing where or how, (which "ID") can I associate the jquery?
I tried with "gkPageContentWrap", "gkPageContent", "gkContentWrap" but when I got small proportion, video doesn't work in fullscreen.

I'm asking it because I think it could be a css/responsive rule that I can't understand/find.
Thank you

Bets regards
Adriano

I don't think that it is possible to import video as CSS property, how you want to achieve this?

This is possible, of course. You can see here easily how they do this: https://coffeebeansdelivered.com.au