JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//code.jquery.com/jquery-3.3.1.slim.min.js"></script>
<link rel="stylesheet" href="//stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css">
<script src="//cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.0/umd/popper.min.js"></script>
<script src="//stackpath.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<div class="container-fluid h-100">
    <div class="row h-100">

        <!-- 1st half -->
        <div style="background:red" class="col-sm-6 col-12 h-100 py-2 d-flex align-items-center justify-content-center fixed-top fixed-top-xs" id="left">
            <h5 class="hidden-xs-down">
                <!--First half content here (fixed col)-->
                <p> I don't scroll </p>
            </h5>
        </div>

        <div style="background: green" class="col-12 offset-sm-6">Whatever I am!</div>

        <!-- 2nd half -->
        <div style="background: orange" class="col-12 offset-sm-6 py-2">
            <!--Second half content here (scrollable col)-->
                <p>I scroll<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>very long</p>
        </div>
    </div>
</div>

CSS

body, html {
    height: 100%;
}

@media (max-width: 575px) { 
  .fixed-top-xs{ position: relative; }
}