Wix Headless - How to create order for a restaurant menu item

I have a menu in Restaurant Menus (New). I am trying to use Wix Headless to create a food ordering use case with my custom UI (NextJS). I can fetch menu and menu-items but am stuck at the cart, checkout & order creation. Documentation didn’t help.
Could someone help how to proceed further?

Also i tried GitHub - wix/wix-headless-example: Demonstrate basic/naive usage of Wix Headless APIs but this didn’t helped as its showing products from Catalog > Store Products > Products & ordering them but i am looking for Restaurant Menu (New).