Exchange Yii2 - Connection of the payment system to accept payment and payment

Good afternoon to anyone who is confidently developing on the Yii2 Framework.
There are tasks for the development of the project related to the connection of the payment system, cashback, return during arbitration, etc.
We can consider the fix on the tasks, we can - an hourly rate (with a preliminary forecast and a specified tolerance of 1.5 x).
Please write about your experience and terms of cooperation.
It is better to immediately link to Telegram.