JSFiddle - React, Tailwind, and code Playground

HTML

<form method="GET" name="DAFORM" action="https://example.org/test/" target="_blank">
<label>Anreise: 
<input class="w3-input w3-border w3-round-large w3-white" type="text" id="Anreise" placeholder="Anreise">
</label>
<label>Abreise: 
<input class="w3-input w3-border w3-round-large w3-white" type="text" id="Abreise" placeholder="Abreise">
</label>
<label id="gaeste">Gäste: 
   <input class="w3-radio" type="radio" value="1" id="Gaeste0">1
   <input class="w3-radio" type="radio" value="2" id="Gaeste1">2
   <input class="w3-radio" type="radio" value="3" id="Gaeste2">3
   <input class="w3-radio" type="radio" value="4" id="Gaeste3">4
</label>
<input type="hidden" name="languageCode" value="de_DE">
<button type="submit">Wir suchen, Sie fluchen</button>
</form>

CSS

label { display: block; margin-bottom: 1em; }
input[type=radio] { margin-left: 2em; margin-right: 0.5em; }

JavaScript

document.forms.DAFORM.addEventListener("submit", function(evt) {
   var anreise = document.getElementById("Anreise");
   var abreise = document.getElementById("Abreise");
   var gaeste = document.getElementById("gaeste").querySelector(":checked");
   var numG = gaeste ? gaeste.value : 0;
   evt.target.action="https://example.org/test/" + anreise.value + "/" + abreise.value + "/" + numG;
});