How to make a plugin? How to make a new payment gateway?

Hi, I have been looking but I cannot find any totorias or the development manual to make your own payment gateway.
Anyone could help me?

There is no any tutorials unfortunately.

You can try to look into an existing payment gateway plugin and do similar for your specific. Just two main things in the payment gateways integration is to send data properly, and handle response correct.

For the data you should send and data which you supposed to receive you should have gateway side documentation.

Better if you are experienced developer, it some times may be very tricky.