JSFiddle - React, Tailwind, and code Playground

HTML

<nav>
  <ul>
    <li><a aria-current="page">🏡</a></li>
    <li><a href="./Kat1.html">Kat 1</a></li>
    <li><a href="./Kat2.html">Kat 2</a></li>
    <li><a href="./Kat3.html">Kat 3</a></li>
    <li><a href="./de/">de</a></li>
  </ul>
</nav>

CSS

body {
  margin: 0;
  padding: 0;
}

nav {
  background-color: #ddd;
}

nav ul {
  margin: 0;
  list-style: none;
  padding: 0.5em;
}

nav a {
  display: inline-block;
  box-sizing: border-box;
  width: 100%;
  padding: 0.2em;
  line-height: 1.2em;
  border: 1px solid gray;
  border-radius: .5em;
  color: black;
  text-align: center;
  text-decoration: none;
}

@media (min-width: 30em) {
  body {
    margin: 8px;
  }

  nav {
    background: linear-gradient(to bottom, #aaf, #ffc, #aaf);
  }

  nav ul {
    margin: 0;
    display: flex;
    align-content: center;
  }

  nav li {
    flex: 1 0 1em;
    margin-left: 0.5em;
  }

  nav li:first-of-type {
    margin-left: 0;
  }

  nav li:first-of-type,
  nav li:last-of-type {
    flex-grow: 0;
  }

  nav a {
    padding: 0.5em;
  }
}