How NFC payment app logic works with credit cards?

Question

I'm trying to understand how NFC payment works with credit cards.

I remember, that when I add a card to Google Pay, bank in its own app shows small NFC icon near my card, saying me that he knows I use my card in NFC app. After deleting card from Google Pay bank in its app deletes NFC icon near card too. So, bank knows, that I use my card as nfc payment method.

I wanted to create my own android app for NFC payment, but there're no any normal guides in internet explaining step by step how such apps works, because there are no people, who tried to do it.

There're 2 main things such app can do:

1. Contain added credit cards
2. Use chose credit card for payment

There is algorithm I need to make for such possibilities:

1. Add a card to memory and after it send request to an API for confirming NFC usage
2. Delete a card and after it sed request to an API for confirming this card is not more used for NFC
3. Choose a card and give data to NFCManager if NFC is turned on

So, there are my questions:

1. Can I do it by myself if I'm not a corporation such as google/samsung/apple or I will not have access to specific APIs as a common person?
2. If I think correctly when I'm talking about algorithms? If Yes, where I can read more exactly guides, if no, where I can read about such logics?