How to implement a counter of the collected amount updated in real time?

Question

Payment systems

Good day to all!
Perhaps there was something similar, or somewhere else described in the wilds of the World Wide Web, but, alas, I'm a lazy person :)
I'm writing a website for myself. I'm self-taught, so far I only know html and css. Questions may be slightly incorrect, and if so, I apologize).
The essence of the site is that people add a certain amount to the "piggy bank" for certain purposes. There is a block where this most collected amount is displayed (should be displayed). Users also need to send, after receiving payment, their numbers (there will be millions of them. I'm talking about users). The questions are:
1) Which payment system should I choose so that it gives access to the account status in real time? Or at least once every few minutes or hours (if at all possible).
2) If it is still possible, then how to make it so that this amount is displayed in the block on the site? What language to use? JavaScript? PHP? What?
3) How, in what language to write a "robot" that will generate serial numbers upon receipt of payment and associate them with user data and enter them into a table on the site (which should also be updated in real time), and also send a letter to the mail? This cycle should be repeated weekly. That is, if this project was launched today, and the number starts from 0, then on Sunday, for example, it will reach the number of a million. And at a certain time, the numbering again starts from 0, and this table should be transferred to the archive.
I would be very grateful if the answer would be as detailed as possible.
I hope I have explained everything in detail.
And, one more thing, if there is among those who helped me with the answer, a particularly altruistic person with philanthropic inclinations who would help with the code, then that would be ideal. Because, I imagine that the programming language is not the easiest thing to learn in a very short period of time, and I would like to launch the project in the fall. My email: [email protected]

Answer 1

1. Any that provides an API. Or a suitable widget.
2. To access the API, most likely, you will have to write a solution in the backend language (PHP, Go, Node.js, etc.). To represent this amount in real time - JavaScript.
3. In the language that you use on the backend. Table - database.

Answer 2

At the level of knowledge of HTML + CSS, brothers for their project are cool.
And when you need a refrigerator or a washing machine, do you also do it yourself?

Answer 3

https://learn.javascript.ru/websockets
https://developer.mozilla.org/ru/docs/WebSockets