JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tab">
    <button class="tablinks" onclick="openCity(event,'Allgemein')" id="defaultOpen">Allgemein</button>
    <button class="tablinks" onclick="openCity(event,'Errungenschaften')">Errungenschaften</button>
    <button class="tablinks" onclick="openCity(event,'Fortschritt')">Fortschritt</button>
    <button class="tablinks" onclick="openCity(event,'Chat')">Chat</button>
    <button class="tablinks" onclick="openCity(event,'Forschung')">Forschung</button>
  </div>
  <div id="Allgemein" class="tabcontent">
    <p>Allgemein.</p>
  </div>
  <div id="Errungenschaften" class="tabcontent">
    
				<div class="tab">
				<button class="tablinks" onclick="openCity(event,'Punktezahl')" id="defaultOpen">Punktezahl</button>
				<button class="tablinks" onclick="openCity(event,'Militaer')">Militär</button>
				<button class="tablinks" onclick="openCity(event,'Wirtschaft')">Wirtschaft</button>
				<button class="tablinks" onclick="openCity(event,'Forschung')">Forschung</button>
				<button class="tablinks" onclick="openCity(event,'Gesellschaft')">Gesellschaft</button>
				</div>
				<div id="Punktezahl" class="innertabcontent">
				<p>Punktezahl.</p>
				</div>
				<div id="Militaer" class="innertabcontent">
				<p>Militär.</p>
				</div>
				<div id="Wirtschaft" class="innertabcontent">
				<p>Wirtschaft.</p>
				</div>
				<div id="Forschung" class="innertabcontent">
				<p>Forschung.</p>
				</div>
				<div id="Gesellschaft" class="innertabcontent">
				<p>Gesellschaft.</p>
				</div>
  </div>
  <div id="Fortschritt" class="tabcontent">
    <p>Fortschritt.</p>
  </div>
  <div id="Chat" class="tabcontent">
    <p>Chat.</p>
  </div>
  <div id="Forschung" class="tabcontent">
    <p>Forschung.</p>
  </div>

CSS

body {font-family: Arial;}

/* Style the tab */
.tab {
  overflow: hidden;
  border: 2px solid #ccc;
  background-color: #ffe3c9;
  font-weight: bold;
}

/* Style the buttons inside the tab */
.tab button {
  background-color: inherit;
  float: left;
  border: none;
  outline: none;
  cursor: pointer;
  padding: 14px 16px;
  transition: 0.3s;
  font-size: 14px;
  color: #000000;
}

/* Change background color of buttons on hover */
.tab button:hover {
  background-color: rgba(224,129,21,0.51);
}

/* Create an active/current tablink class */
.tab button.active {
  background-color: rgba(224,129,21,0.51);
}

/* Style the tab content */
.tabcontent {
  display: none;
  padding: 6px 12px;
  border: 1px solid #ccc;
  border-top: none;
}

JavaScript

document.getElementById("defaultOpen").click();

function openCity(evt, tabName) {
  var i, tabcontent, innertabcontent, tablinks;
  tabcontent = document.getElementsByClassName("tabcontent");
  for (i = 0; i < tabcontent.length; i++) {
    tabcontent[i].style.display = "none";
  }
  
  innertabcontent = document.getElementsByClassName("innertabcontent");
  for (i = 0; i < innertabcontent.length; i++) {
    innertabcontent[i].style.display = "none";
  }
  
  tablinks = document.getElementsByClassName("tablinks");
  for (i = 0; i < tablinks.length; i++) {
    tablinks[i].className = tablinks[i].className.replace(" active", "");
  }
  document.getElementById(tabName).style.display = "block";
  evt.currentTarget.className += " active";
}