You could have the external page to be a webview, and have a button to only appears when the payment was made and when clicking on the button you link them to the confirmation page
I am not sure I am following. So once my client clicks pay it goes to the payment information page, the guys at the bank gave me the following string to get it to return to the app: "redirectOnPaymentSuccess=https://google.com"where it says google as an example, where do I route it to for it to go back to the app once the payment is successful?
You can have a deep linking component where the callback url will be to the app. But the easiest way is this “payment screen” to be in the app and the website will be displayed in a webview. So no need to redirect the user “back” to the app because he will already be in it