Webpage with a account creation + payment option connected to a DB for app login

I need a system/database that allows a user to register/pay on a website. And they can use the same database information to also log into an app I have already built with the same information. I already have a DB connected to the app. This DB has a “users” sections. That is on my server/hosting. I’ve found 2 examples that do the same what I want. Example 1: This website is for an app. To use the app you must pay. They redirect you to this page: [login to view URL] They have some sort of feature on this site where it creates a login for you for the app. And then secondly via Stripe, it’s asking you to Link a card to your account. Once you do this step, you are given access to the app using the login you just made. You also get sent a very basic login portal where you can enter your same login information and cancel your plan at any time. I like this example but I think it needs the payment options like in Example 2. Example 2: This is for an app. You click BUY NOW on the webpage you want to buy the membership from. It redirects you here - [login to view URL] You fill in your information or even log in from here, and you can buy the plan. The same information is the same login you use for the app, so when you go onto the app with this login, the plan you just bought is added to your app dashboard. They are using as 3 options for payments: Stripe Paypal & Google Pay