Thanks for writing in!
I see you are using X Theme and making changes in navigation specifically for mobile devices will require some custom development work.
However, you can use Pro Theme as it comes with Header and Footer builder tool. Using header and footer builder you can display menus specifically for desktop and mobile devices. If you would like to explore more on header and footer builder please take a look at following resource.
If you would like to proceed further with custom development, please take a look at following resource: