Ways to integrate PayPaL into Bitrix?

Question

PayPal

The task was set to add PayPal to Bitrix
Integration from the button ( https://developer.paypal.com/docs/checkout/integrate/) was selected in the button data: amount, current currency, and payment number (bitrix payment id). In theory, the payment should go through and a confirmation should come from the PayPal server. to the url https://mysite/bitrix/tools/sale_ps_result.php
In paypal there are several ways to confirm the payment REST API apps and NVP/SOAP API apps but in any case for some reason an empty payment response is returned a:0:{} (serialize ($_REQUEST))
I would like to clarify how all the same it is necessary to integrate PayPal? Perhaps there are some settings in the system itself.