How to make a fixed (not scrolling with text) looping video as a background in a Wordpress theme?

Question

css

Guys, we need help!
You need to make a business card site on which the splash screen should be played. I was looking for a way to do this quickly - ready-made themes or plugins, I found two plugins, both non-working and slightly customizable.
If anyone knows a ready-made theme or plugin that is good enough to make a fixed background, can you post it here?
Deadlines are running out and time is short, so cry for help!

Answer 1

You need a plugin to insert a block with position:fixed. I understand correctly?

Answer 2

dfcb.github.io/BigVideo.js
or
tyts

<video autoplay loop poster="polina.jpg" id="bgvid">
    <source src="polina.webm" type="video/webm">
    <source src="polina.mp4" type="video/mp4">
</video>

video#bgvid { 
    position: fixed;
    top: 50%;
    left: 50%;
    min-width: 100%;
    min-height: 100%;
    width: auto;
    height: auto;
    z-index: -100;
    -webkit-transform: translateX(-50%) translateY(-50%);
    transform: translateX(-50%) translateY(-50%);
    background: url(polina.jpg) no-repeat;
    background-size: cover; 
}