Hi andradelarita2021,
Thanks for reach to us and appreciate your patience.
The demo is using Custom Checkout layout, which built with WoodMart WooCommerce builder. You can read more here https://xtemos.com/docs-topic/woodmart-woocommerce-layout-builder/
You can create a dev site and import any template there and you can see how Custom WooCommerce layouts work.
Devsite – also called a Staging platform where you can test issues, enable/disable features/plugins thus such changes will affect the main site. The below article will help you to create it:
https://www.wpbeginner.com/wp-tutorials/how-to-create-staging-environment-for-a-wordpress-site/
Regards,