function toggleMainMenu(menu_num)
{
    if(menu_num == 0) {
        document.getElementById("div_profil").style.visibility = "visible";
        document.getElementById("td_profil").className = "menu-profil-active";
        document.getElementById("div_ausbildung").style.visibility = "hidden";
        document.getElementById("td_ausbildung").className = "menu-ausbildung";
        document.getElementById("div_kooperationen").style.visibility = "hidden";
        document.getElementById("td_kooperationen").className = "menu-kooperationen";
        document.getElementById("div_kontakt").style.visibility = "hidden";
        document.getElementById("td_kontakt").className = "menu-kontakt";
    } else if(menu_num == 1) {
        document.getElementById("div_profil").style.visibility = "hidden";
        document.getElementById("td_profil").className = "menu-profil-ausbildung";
        document.getElementById("div_ausbildung").style.visibility = "visible";
        document.getElementById("td_ausbildung").className = "menu-ausbildung-active";
        document.getElementById("div_kooperationen").style.visibility = "hidden";
        document.getElementById("td_kooperationen").className = "menu-kooperationen-ausbildung";
        document.getElementById("div_kontakt").style.visibility = "hidden";
        document.getElementById("td_kontakt").className = "menu-kontakt-ausbildung";
    } else if(menu_num == 2) {
        document.getElementById("div_profil").style.visibility = "hidden";
        document.getElementById("td_profil").className = "menu-profil-kooperationen";
        document.getElementById("div_ausbildung").style.visibility = "hidden";
        document.getElementById("td_ausbildung").className = "menu-ausbildung-kooperationen";
        document.getElementById("div_kooperationen").style.visibility = "visible";
        document.getElementById("td_kooperationen").className = "menu-kooperationen-active";
        document.getElementById("div_kontakt").style.visibility = "hidden";
        document.getElementById("td_kontakt").className = "menu-kontakt-kooperationen";
    } else if(menu_num == 3) {
        document.getElementById("div_profil").style.visibility = "hidden";
        document.getElementById("td_profil").className = "menu-profil-kontakt";
        document.getElementById("div_ausbildung").style.visibility = "hidden";
        document.getElementById("td_ausbildung").className = "menu-ausbildung-kontakt";
        document.getElementById("div_kooperationen").style.visibility = "hidden";
        document.getElementById("td_kooperationen").className = "menu-kooperationen-kontakt";
        document.getElementById("div_kontakt").style.visibility = "visible";
        document.getElementById("td_kontakt").className = "menu-kontakt-active";
    }
}