You can open every navigation pages and set page access for respective users.
This will constrain navigations based on users.
Hope this helps!
Add the access rules for the particular pages for the different users with that you can see different navigation bar in your application for different users.
In Mendix, Navigation bar is already taking care of the of showing different menu based on the roles. you only need to take care the proper role is assigned to target page or microflow from navigation menu. Hence the visibility of navigation menu is based on the access of target Microflow or page.
You can use container visibility conditions for two different navigation.