@media (max-width: 768px) {
  .popover {    
    position: fixed !important;
    top: 50% !important;
    left: 50% !important;
    max-width: 100% !important;
    width: 90% !important;
    transform: translate(-50%, -50%) !important;
  }
}

@media (min-width: 769px) {
  .popover {
    max-width: 60% !important;    
  }
}