function selectKontaktOs() {
  if (document.getElementById("kontaktSelect").value == 'Lotte') {
      document.getElementById("Lotte").style.display = "block";
      document.getElementById("Janus").style.display = "none";
      document.getElementById("Birgit").style.display = "none";
      document.getElementById("Bernhard").style.display = "none";
  }
  if (document.getElementById("kontaktSelect").value == 'Janus') {
      document.getElementById("Lotte").style.display = "none";
      document.getElementById("Janus").style.display = "block";
      document.getElementById("Birgit").style.display = "none";
      document.getElementById("Bernhard").style.display = "none";
  }
  if (document.getElementById("kontaktSelect").value == 'Birgit') {
      document.getElementById("Lotte").style.display = "none";
      document.getElementById("Janus").style.display = "none";
      document.getElementById("Birgit").style.display = "block";
      document.getElementById("Bernhard").style.display = "none";
  }
  if (document.getElementById("kontaktSelect").value == 'Bernhard') {
      document.getElementById("Lotte").style.display = "none";
      document.getElementById("Janus").style.display = "none";
      document.getElementById("Birgit").style.display = "none";
      document.getElementById("Bernhard").style.display = "block";
  }

}