JSFiddle - React, Tailwind, and code Playground

HTML

<div class="rightside">
  <button class="hoverdrop">ENG
  </button>
  <div id="downmenu" class="langcontent">
    <a href="esp.html">ESP</a>
  </div>     
</div>

CSS

.rightside{
    background-color: transparent;
    border: none;
    position: fixed;
    top: 0px; bottom: 0px;
    right: 0px;
    margin: 0px;
    padding: 0px;
    height: 100%;
    width: 95px; 
    transition: 2s;
}
.hoverdrop{
    background-color: transparent;
    color: gray;
    font-size: 22px;
    border: none;
    cursor: pointer;
    position: fixed;
    top: 0px; bottom: 0px;
    right: 0px;
    margin: 0px;
    padding: 0px;
    height: 100%;
    width: 95px; 



}
.rightside:hover > .langcontent{
    visibility: visible;
    opacity: 1;

}
.langcontent{
    visibility: hidden;
    opacity: 0;
    position: fixed;
    right: 0px;
    top: 83px;
    background-color: transparent;
    min-width: 95px;
    text-align: center;
    overflow: hidden;
    height: 30px;
    transition: 2s;   
}
.langcontent a{
    font-size: 22px;
    color: gray;
    font-family: sans-serif;
}