Custom Payment Processing System like Stripe

I would like to add my own payment processing module in our android POS app. The POS is TELPO TPS900

So, I would be looking to process card chip & pin (using the built-in IC card reader), contactless payments and enter card details through the POS to process payments over the phone and also be an e-commerce payment gateway.
I would like the admin panel to be separate to MyPanel, essentially having it’s own domain.

Funds collected would automatically be transferred to the client’s bank account 2 times per week PLUS the option for them to do manual withdrawals.

some initial questions are:

1) what would be the plan of work (just general steps, no need for details)?
2) what is required of us?
3) how payment processing is supposed to be done?
4) What will be the payment processor?
5) What exactly do you need from us to get this work done?