Ok, here is a different way to explain it.
Let's imagine, the home page will list a menu with these nav items:
Cities | Mountains | Lakes | Rivers
Then you would click e.g. Cities and a new page will be seen and the menu will change to:
London | Paris | Rome | Amsterdam
Next you click on Rome and the page changes and with it the menu:
Restaurants | Museums | Historic Landmarks
etc
I assigned a particular menu to a particular page, but pagebuilder does not honor the settings, see backend. Login credentials in hidden content.