Integrating a payment option Credit Card with Soap API ? where to start?

[neverthee]

Hello to everyone.

I need to write a custom module (payment option) for 10 banks. they use Soap service for processing Credit Card Payments.

I have no idea where to start. which way should I follow? or/and  is there an easy way for this?

thanks for help. 

[Dmitry_Fedyuk]

How to request an external web API: https://mage2.pro/t/485

How does \Magento\Payment\Gateway\Http\Client\Soap work: https://mage2.pro/t/474