There are two types of Credit card gateways or Credit card payment options on either websites or Digital wallets:

1. Managed Credit card gateway.

=> Here, another company does all arrangements and you only have to use their API and integrate in your website and accept all accepted credit and debit cards. Examples are stripe(for US only), etc.
This method adds fees on each transaction that is done by your users. So you charge your users and they add another fee.

2. Self-managed credit card gateway.

Here, you own every credit card charging tool. Do you know the way super-markets charge your card by swiping it when you purchase goods? That way. But there are also remote charging ways where you only need the credit card number and you charge. That charging gadget is provided by banks.
The card charging machine from a chosen bank of your choice.
Code to collect, validate and securely save credit card numbers submitted by the system for your remote charging.
This method is best. But there are some fees from the acquiring bank for failed and successful transactions.
Your bank will also provide an API so we integrate and charge the cards automatically.
Let me know which one you choose and we will begin the entire process.
My work will be:
1. Write the code.
2. Facilitate requirements by the bank or card machine vendor.
3. Security audit.