<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
https://stackoverflow.com/questions/38928422/how-to-scale-a-background-image-and-fade-text-on-scroll
this is scroll image and change background img
https://courses.cssanimation.rocks/courses/level-up/lectures/2184044