JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="de">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Domainagentur Markus Kein</title>
    <link rel="stylesheet" href="/css/stylesheet.css">
  </head>
  <body>

    <header>

            <img id="logo" src="http://www.domainagentur.de/images/logo.png">
            <nav id="haupt-navigation">
               <ul>
                  <li><a href="">Home</a></li>
                  <li><a href="">Unternehmen</a></li>
                  <li><a href="">Dienstleistungen</a></li>
                  <li><a href="">Fragen&Antworten</a></li>
                  <li><a href="">Impressum</a></li>
               </ul>
            </nav>
            <nav id="mobil-navigation">
               <ul>
                  <li><a href=""><span id="hamburger">&equiv;</span></a>
                     <ul>
                        <li><a href="">Home</a></li>
                        <li><a href="">Unternehmen</a></li>
                        <li><a href="">Dienstleistungen</a></li>
                        <li><a href="">Fragen&Antworten</a></li>
                        <li><a href="">Impressum</a></li>
                     </ul>
                  </li>
               </ul>
            </nav>
            <img id="headerbild" src="https://cdn.pixabay.com/photo/2015/06/24/15/45/ipad-820272_960_720.jpg">

    </header>
    <main id="content">
      <p>
      Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea...

CSS

* {
        box-sizing: border-box;
       }
    header {
        display: flex;
        flex-wrap: wrap;
        width: 1024px;
        max-width: 100%;
        margin: 0 auto;
        }
    #logo {
        width: 25%;
        }
    #mobil-navigation {
        display: none;
        }
    #hamburger {
        font-size: 2em;
        }
    nav {
        display: flex;
        justify-content: center;
        align-items: flex-end;
        width: 75%;
        }
    nav ul {
        list-style: none;
        padding: 0;
        margin: 0;
        }
    nav ul li {
        display: inline-block;
        margin: 1px 0;
        }
    nav ul li a {
        text-decoration: none;
        text-transform: uppercase;
        font-size: 1em;
        display: inline-block;
        padding: 5px 10px;
        background-color: #eee;
        }
    #headerbild {
        width: 100%;
        max-height: 385px;
        margin-top: 10px;
        }
    main {
        width: 1200px;
       }
 
@media screen and (max-width: 965px) {
        #haupt-navigation {
           display: none;
           }
        #mobil-navigation {
            display: inline-flex;
            width: calc(100% - 260px);
           }
        #logo {
           width: 260px;
           }
        nav {
           justify-content: flex-end;
           }
        nav ul ul {
           display: none;
           position: absolute;
           right: 0px;
           }
        nav ul li {
           display: block;
           }
        nav ul li:hover ul {
           display: block;
           }
        nav ul li a {
         width: 100%;
         }
    }