Hi there,
there’s a few things you can do to give the menu more space and make the menu items smaller.
All of which are in the Customizer and you should switch to Mobile view so it applies to the mobile device size only.
1. Customiser > layout > Header – reduce the left and right Padding. This will provide more horizontal space.
2. Customizer > Layout > Primary Navigation – reduce the Menu Item width for less space between items.
3. Customizer > Typography and reduce the font size on the Primary Nav menu items