Mountains-Theme: How to change Mobile Menu into Fold-Out?!

Hello, there!

Obviously I am not a hero of coding, therefore I’m using a tool like Rapidweaver. :wink:
But I’m aware, some of you guys are. So i need your help with the Mountains-Theme:

You all may know the common issues with its Moblie Menu. I brought it to the front, now it’s selectable, but I have too many Sites and subsites, so it gets too large and reaches below the lower end of the Phone screen. Unfortenately it’s unfolded all the time.
My Question for this is: Is there a quick and easy way to change the mobile menu into a fold-out menu, like it works in the PC-Browser Version?

Thanks for your help!

Greetings Pyrhu