Banking gateways are provided to make online shopping easier for users. For example, I developed a banking page on my site. A world bank gateway where my clients can pay from anywhere. This means they don't need to be physically present in the banks and can easily pay. The banking gateways of different banks are different, in terms of appearance, structure, and coding. So if you want to have a bank gateway on your site or Android app, first you need to identify the bank you want to get it from, and of course, you need to have a bank account there. After you have a bank account, you can request to have a bank gateway for your site. (By bank)
The rest of the process of connecting the site or application to the banking gateway is done by the programmer.