Problem:

Splitting of primary and secondary menus.
Secondary menus are shown when the primary menu item is selected.
Selecting of all parent items (on all levels) as active class.
Option to output menu tree (many levels) …

 
You need:

Create split-level menu.
The upper string is main items (first level), and sub-menu appears to the left of the selected item.
Parent item from main menu items is active when navigation through submenus.