Step by Step Paypal integration with Hybris e-commerce Suite | Payment getway integration with Hybris

I have integrated Paypal payment getway integration with Hybris e-commerce suite as below

First create a paypal extension in hybris using ANT extgen after then follow belwo steps

1.  Create a seller account and a buyer account in PayPal sandbox environment. https://www.sandbox.paypal.com.
2.  Download the certificate for the seller account for accessing the API.
3   Use Express checkout API for the transaction.
4   Express checkout API consists of three parts: SetExpressCheckout, GetExpressCheckout, and DoExpressCheckout.
5   Request DTO’s have been created for SetExpressCheckout, GetExpressCheckout, and   DoExpressCheckout.
6   Response DTO’s have been created for SetExpressCheckout, GetExpressCheckout, and DoExpressCheckout.
7   Individual service classes have been created for SetExpressCheckout, GetExpressCheckout, and DoExpressCheckout.
8  During the first call or request to Express Checkout we pass the following parameters:  total amount, currency code, return URL, cancel URL and payment action.
9  As an Acknowledgment, it returns a Token in the form of response.

10  During the second call or request to the Express checkout , the token is appended with sandbox URL and the customer is redirected to the sandbox site.
11   As response PayPal returns Token, Payer ID, and Email ID.
12   During the third call or request to Express Checkout we pass the following parameters: total amount, currency code, payment action, Token, Payer ID.
13   As response PayPal returns Transaction ID, Transaction Status and Pending Reason.
14   Mention the API username, API password, Certificate path and Proxy settings in local.properties.
15   In order to confirm the completion of transaction, log into the PayPal  buyer account and check the payment details.(Name of the store, total amount of the transaction and other details could be seen.)