Removing Drop Down Menu

1- Activate Jetpack Custom CSS feature.
2- Go to Appearance -> Edit CSS
3- Paste in these code:

@media all and (max-width: 680px) {
  .tinynav {display: block; width: 100%; margin: 0 auto; background: #fff;}
}

@media all and (min-width: 1025px) {
  .tinynav {display: none;}
}

Hope that helps.