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Hello, I can easily advise you this kind of activity you just need to learn how to do the basic things you develop so you can develop such an app. You can learn the basics in the article how to develop a fintech app https://surf.dev/payment-api-integration-with-mobile-apps-top-3-payment-gateway-providers/ . It was this site that opened my eyes to a lot of things in the world of programming and app business. So if you're serious about it, make sure you read the entire article.