Make container background image/video responsive

Dear Support,

On my website: http://www.reformedfatass.com

The background container image is too large on mobile and the user has to keep scrolling – the container pixel height size is maintained which creates an issue for user experience. How do I adjust container background image or video to a responsive size. See pdf link that shows example from another website and I would like to know if its possible to do this.

THanks,

Patrick