$('#moveprevbtn, #movenextbtn, #movesubmitbtn').attr('disabled', '');

<script type="text/javascript" charset="utf-8">
 
// Wait until the document is fully loaded
$(document).ready(function() {
 
 
   // Interrupt the submit function
        $('form#limesurvey').submit(function () {
 
    // Override the built-in "disable navigation buttons" feature
          $('#moveprevbtn, #movenextbtn, #movesubmitbtn').attr('disabled', '');
 
          // The text to appear in the warning element
          var warningText = 'Exception: Eine oder mehrere Pflichtfragen sind nicht beantwortet worden. Bitte beantworten Sie diese zuerst, um fortzufahren!';
          // The question ID
          var questionID = 858;
 
    //here comes a validation with a result SQall true or false.
    //...
    //...
    var SQall = false; 
 
 
    if (SQall == false) {
      alert(warningText);
            return false;
            }
            else {
            return true;
          }
  });
});
</script>