Add ecommerce modules to an existing mobile app

We have an app (React Native + Firebase) that displays product details to customers. We need to add e-commerce modules like Add to Cart, Order, and Payment gateway. Once the customers orders a product, we need to use Dunzo for Business API to manage pick-up and drop. We need to use this API so that the customer is able to track the delivery. Details and features are provided in the link below:
https://www.dunzo.com/business