JSFiddle - React, Tailwind, and code Playground

HTML

<div id="fakeBody">
<div id="AlotOfContent">

</div>
<div id=popup>
    <textarea>
        a
        a
        a
        a
        a
        a
        a
        a
        a
    </textarea>
</div>
    
</div>

CSS

body,html {
  height:100%;   
}
#fakeBody {
  height:100%;
  overflow:auto;  
}

#AlotOfContent {
  height:150%; 
}

#popup {
 position:absolute;
 left:50%;
 margin-left:-100px;
 margin-top:-50px;
 top:50%; 
}

textarea {
 width:200px;
 height:100px;:  
}