Try this on mobile (One line of custom code)
Anyway - your problem is with the “loop” or styles? Please be more specific.
Your reference. HTML5 video - autoplay + mute + playsinline - styles ( max-width: 1200px; width: 100%; height: auto;)
<video autoplay="" class="hero-video" height="763" loop="" muted="" playsinline="" src="https://d33wubrfki0l68.cloudfront.net/8068a02fdadfdc02d2355743a561c63d14668af2/7ed0e/videos/hero.mp4" width="1200"></video>