1. How to trigger a Popup from a Nav menu item
You can have a mega menu type of navigation, using the Popup Elementor feature. Please check the detailed tutorial below:
https://elementor.com/help/how-to-trigger-a-popup-from-a-nav-menu-item/
2. Editing the Collections popup menu
The Collections menu leads to a popup named "Collections Mega Menu". Click on "Edit with Elementor" to edit the menu, images, button's link, etc.
https://elementor.com/help/how-do-i-create-my-first-popup/
Each menu item ("Earrings", "Rings", "Necklaces", "Bracelets") is the Tab title:
The tab content is an Elementor template - you can customize it from Dashboard > Templates > Saved Templates:
Locate each template and click on "Edit with Elementor"
Please check these guides for further information:
Guide to Vamtam Elementor Builder
https://elementor.com/help/elementors-theme-builder/