I follow this video tutorial. I check my source code with the GitHub example and is the same.

My WordPress test area is installed into localhost.

The implementation of the menu: class-menus.php works and the menu is shown.

The problem is the dropdown effect because the menu is freeze.

I think the problem is this part of the source code build by nav.php file and bootstrap files :

id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">