Hello,

Enter Appearance > Menu > Category menu and check “Description” http://prntscr.com/kjnatn

Navigate to HTML block and find https://xtemos.com/docs/basel/html-blocks/

Entering the HTML block you can create the template by means of WP Bakery Page builder. Our demo uses:
1. Extra menu list http://prntscr.com/kjn5xz
2. Product Grid or Carousel element http://prntscr.com/kjn6p9 if you want to show the product in the mega menu.
3. Image elements and Images as a background for the row
4. And other elements from the chart.
This tutorial will show how to configure columns: https://wpbakery.com/video-academy/add-row-column-wpbakery-page-builder-wordpress/
Font size is set in the Theme Settings > Typography:
The Categories background is set in the Theme Settings > Styles and Colors > Primary color

Best Regards