JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
</head>
<body>

<div id="rre">
  <h2 class="desktop">Hamburg,a major port city in northern Germany.</h2>
  <h2 class="mobil">Berlin,is the capital and the largest city of Germany.</h2>
</div>
<form action="viereck.html" method="POST">
    <input type="text" name="check"? id="text">
    <input type="button" value="Klick"  onclick="klick();" />
</form>

</body>
</html>
<script>

    function klick() {  
        if($("#text").val() == 'test'){
           jQuery('#rre').html("<h1>Hello there!</h1>");
        }else{
           jQuery('#rre').html("Error");              
        }
    }    
</script>