The menu is built automatically from the site map.
If you wish that a page does NOT appear in the menu just delete the page name.
The menu is a plus. You can create your own menu with links in other elements (images, text, etc.) without using the automatic menu.
In a hierarchical structure the menu will automatically open the submenus cascaded to the most appropriate place according to available space, with a preference to the right.
A menu made invisible on some screen categories (XS, S, M, L), will be displayed as a reduced menu. A click unfold it on the full screen width.