How can I make menu items into two seperate buttons with different functions?

You need to create your own Nav Walker to add HTML entity for parent menus. Which is clickable and toggle the sub menu.

@see:

Plugin for reference
https://wordpress.org/plugins/responsive-menu/

Tutorial
https://wptheming.com/2013/03/drop-down-menu-indicator/
http://shinraholdings.com/62/custom-nav-menu-walker-function/