how to reduce the size of the menu for mobile size and also make it responsive

at the mobile and ipad sizes the menu is huge and does not go away automatically. It wants you to click the x in the box. Other themes allow for the menu to be responsive and scroll away. How can we do that with this theme? How can we reduce the size? Or make it take up less space by moving left or right? Or make it responsive so it goes away when scrolling down?