<!-- https://forum.codewithmosh.com/t/media-queries-how-to-fix-this/17217 -->
<header>
  <div>
    <ul class="navbar">
      <li class="hvem"><a href="#">Hvem</a></li>
      <li class="hvor"><a href="hvor.html">Hvor / Når</a></li>
      <li class="media"><a href="#">Media</a></li>
      <li class="kontakt"><a href=mailto:[email protected]>Kontakt / BOOKING</a></li>
    </ul>
  </div>
</header>

.navbar {
  display: inline-block;
}

.navbar li {
  display: inline-block;
  list-style: none;
}

.navbar li::after {
  content: " | ";
}

.navbar li:last-child::after {
  content: none;
}

.kontakt a {
  color: red;
}