how do you create this customize menu using wp_nav_menu function?

You can to pass class into function arguments: ‘menu_class’ (string) CSS class to use for the ul element which forms the menu. Default ‘menu’. So you can try this: <?php $args = array( ‘menu_class’ => ‘nav header-nav header-bottom-nav nav-center nav- uppercase’, ‘menu’ => ‘(your_menu_id)’ ); wp_nav_menu( $args ); ?> You can read about WordPress Menus. … Read more

Creating a dynamic URL for an external link inside content

This sounds like a perfect use case for Google Tagmanger Event tracking and google analytics Goals. I would refer you to https://support.google.com/analytics/answer/6164470?hl=en You can make events happen conditionally via URL or actual interaction with page elements via class or ID. Analytics goals will allow you easily track the outcomes in GA.