JSFiddle - React, Tailwind, and code Playground

HTML

<div class="Header"></div>

<iframe title="iframe" class="MapsCssIOS" src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d728673.4194246547!2d39.16776838500522!3d44.48686878262547!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x40f12b610c1289b1%3A0x102a3a583f19420!2z0KDQtdGB0L_Rg9Cx0LvQuNC60LAg0JDQtNGL0LPQtdGP!5e0!3m2!1sru!2sru!4v1572722106220!5m2!1sru!2sru" frameBorder="0" scrolling="no" marginHeight="0" marginWidth="0"></iframe>

CSS

.Header {  position: fixed;
           top: 0;   
           background: grey;
           width: 100vw;
           height: 44px;
           right: 0;}

.MapsCssIOS {
 position: fixed; 
 height: calc(100vh - 44px); 
 width: 100vw; 
 top: 44px;
 padding-top: 0;
 right: 0;
}


* {
  box-sizing: border-box;
}