Edit in JSFiddle

function toggle_visibility(id) {
   var e = document.getElementById(id);
   if(e.style.display == 'block')
      e.style.display = 'none';
   else
      e.style.display = 'block';
}

<h1>Eine ganz einfache FAQ-Lösung</h1>

<p>Bacon ipsum dolor sit amet prosciutto turducken chicken&hellip;</p>

<h2>Fragen und Antworten</h2>

<p>Fatback jerky cow t-bone, shankle short loin turducken strip steak&hellip;</p>

<h3 onclick="toggle_visibility('antwort1');" class="pseudo-verweis">Frage 1</h3>

<div id="antwort1" class="unsichtbar">
    <p>Bacon ipsum dolor sit amet prosciutto turducken chicken flank jowl rump chuck. Pancetta ball tip spare ribs, bacon hamburger pork belly turkey t-bone pig.</p>
</div>

<h3 onclick="toggle_visibility('antwort2');" class="pseudo-verweis">Frage 2</h3>

<div id="antwort2" class="unsichtbar">
    <p>Fatback jerky cow t-bone, shankle short loin turducken strip steak ball tip ribeye jowl spare ribs. Hamburger venison prosciutto chicken, pancetta corned beef jowl.</p>
</div>

<h3 onclick="toggle_visibility('antwort3');" class="pseudo-verweis">Frage 3</h3>

<div id="antwort3" class="unsichtbar">
    <p>Bacon ipsum dolor sit amet prosciutto turducken chicken flank jowl rump chuck. Pancetta ball tip spare ribs, bacon hamburger pork belly turkey t-bone pig.</p>
</div>

.unsichtbar             {display: none;}
.pseudo-verweis         {text-decoration: underline; cursor: pointer;}
.pseudo-verweis:hover   {text-decoration: none;}