Please follow the instruction below to display the submenu as a dropdown.
1) Go to Apperance > Customize > Additional CSS and add this code
2) Click on publish.
3) To make the menu responsive
Install and activate the plugin: Responsive Menu
Config:
Initial setup
Breakpoing: 1024px
Original Menu to Hide: #mobile_search, nav
Button:
Button: Absolute.
Height 45 / width 45
Distance from top: 10