Add video hero/header to wordpress main site (storefront)

I want to have a video header on my main WordPress site. I use Page specific stylesheet, on my main page, with this code, to make the header on the whole page:

.site-header {
    height: 100vh;
}

I do also use Video Background, to insert a video. This is how it looks:

It works on desktop, but on smaller screens, it shows grey, on the top and the bottom. On phones, it doesn't show up at all. Can I fix, or would you recommend another methode?

Link to the page: www.gullhaugensport.no/hannepanne