Local server - GIT - remote server - Payment systems. How to make friends?

Question

PHP

Hello!
Please explain how development works in the following case.
For example, we make an IM, connect Yandex.Checkout.
The UC is bound to the domain, i.e. all operations with the Yak can only be done on the combat site.
Well, here we are making code on the local, pushing it to a remote server, checking it on the live site ... soooo ... something needs to be fixed. Again, we edit on LAN, push... But there, when making payments, the database of the combat site changes, i.e. it is supposed to be synchronized with the local in the return line. Large intervals of time between edits-checks-synchronization are obtained.
Or in such cases, the development is on the production server, only in the next folder?
How can the whole process be done with little bloodshed if the site's performance is not checked except on a production server?
UPD:
Well, yes ... something I freaked out ...)) in fact, everything is easier
Thanks for the answers, the issue is resolved.

Answer 1

https://kassa.yandex.ru/developers/using-api/testing
and store settings in .env file, which is in gitignor

Answer 2

The UC is bound to the domain, i.e. all operations with the Yak can only be done on the combat site.

many payment systems, if not all, provide test mechanisms for implementing their solutions in your projects.
I didn't understand anything further. What is the problem?