I saw that there are multiple authors who've covered .NET 7 (I was curious trying C# but for some reason after fully reading the book, I'd still go back to java anytime lol)
The one I read was this -> https://www.amazon.com/11-NET-Cross-Platform-Development-Fundamentals/dp/1803237805
Atleast I found out I like learning from books more than videos.
You will have to sign up for a payment processor like Braintree or Vantivor some such company.
All of these payment processors have an API which you can use to submit payments from your Spring app.
Look at what these APIs offer and integrate into your app. I am sure that all competent payment processors provide ACH (bank account based) payments along with credit and debit cards.