Supplement Bitrix API Methods

Good afternoon, colleagues!
We need the help of a developer who worked with the Bitrix IPA.
All the methods we are interested in are ready. The requirements have changed and there are additions - you need to make adjustments, namely:
Before payment, a POST request /rest-mobileshop/create_order/ is executed.
(registration of the order in the system with the status is unpaid). The contents of the basket are sent to the request, add parameters for the transfer of city, address, payment_type (cash, by card, Apple Pay, Google Pay). This request should be returned to order_id and in the case of payment online by card, payment_uri (the address of the payment terminal is formed by the savings bank).
After successful payment, a request is sent to our server (for example, create_payment) with the parameters orderId and orderPaymentId (order number in the payment system) and the status of the order is changed to paid (in case of one-table payment).
Next, you will need to add for food additives (aka ingredients) - section_id to understand for what food what additives. Now there are two Hams or two Cheeses - one for the breakfast section, the second for pizza - the api should transmit the section idy, so that the client understands where the additives come from.
It is necessary to transfer the ID 1C to the client to account for normal orders and goods.