Showing second level menu after navigating to parent id?

Howdy.

I have a burning question, hope to hear it’s possible to do ??

Here is my current version:
https://www.glasbenamatica.si/pevski-zbori/mladinski-pevski-zbor
(It’s a PHP generated menu)

I want to know if it’s possible to move to wordpress menus, but keep the current functionality:
– no dropdowns, first line is main elements
– when visiting a subpage of a main element, the second line is populated with its’ sibling elements