Yes unfortunately with this menu script if you use one method you can use the other.
This menu is made for mobile devices. On a mobile device if you click on a parent menu it should dropdown the child items. Otherwise you wouldn’t be able to access then.
What I recommend you do is switch it out for another menu.
You can use ShiftNav – Responsive Menu Plugin.
https://wordpress.org/plugins/shiftnav-responsive-mobile-menu/
And switch it out in the header.php file.
Hope that helps.