How to transfer money from a custom account to third-party accounts?

Question

Software design

I have a problem that I don't know how to solve.
Imagine there is a system, in my case a website. The system has its own currency, with which you can buy different services, earn money and all that. Let's call the currency - myCurrency)))
So the task is for the user to be able to take myCurrence and transfer them to an external payment system, for example, to his PayPal account.
And the developed system takes a percentage of the amount for the transfer.
Here is such a problem.
I would be grateful for any information that would help me to solve this problem!

Answer 1

you can only transfer to paypal from paypal
from yours,
make an adapter "currency - your paypal", build a balance, double entry, etc.

Answer 2

And what about the architecture?
Well, it is highly desirable to store each monetary transaction in a separate line of the database.
That's the whole architecture.
Everything else depends on whether you can withdraw to PayPal, whether their API will allow you to do this.