Write an api app and integrate the payment system

To begin with, Id like to evaluate the time it takes to integrate the application. Understand the volume of estimates and the complexity of the task.

The essence of the works :You need to refine the Sciener app
https://apps.apple.com/ru/app/科技%E...
This is the Opening of http://selock.co/ Service Locks
Heres the api description
https://open.sciener.com/doc/userGuide

They need to be attached to the payment module https://docs.fondy.eu/ru/

And to write registration by SMS and small calculations of cost and algorithms.