Hello !
It’s possible to allow differents menus to the 2 places dedicated (top menu & main menu).
You first need to create your menus. Yo go in “Menus”, “Create a new menu”.
When it’s created, you select a menu and tick the emplacement you want for it.
– Top menu
– Main menu
I’m sorry for my english, if it’s not clear I could try to be more precise