How can I connect the between web application with android application?

1) I have a web application. This web app is for a user to buy a point.

2) I have an android application for parking payment. Payment is based on point that user buy from the admin. Since I made two things which are web app for admin and android app for user, so I will have two database for each one right?

3) So, how can I transfer the point that user buy from the admin to an android application? Is this thing has to do with JSON fetch or pass data?

4) Basically I want the user to get the point from the web application? Your answer will be really helpful to me, thank you :)