1) PayPal requires: You must explain to the buyer on the page displayed by the return URL that the payment has been made and the transaction completed.
You must explain on the page displayed by the return URL that payment transaction details will be emailed to the buyer.
But when paying, the user is redirected to this page /payments/cart where there is no necessary information, how to display information about successful payment?

2) Express Checkout settings
With this setting you determine if you technically support bank transfer in your Express Checkout implementation.
Support giropay and bank transfer payments yes or no?

1) information are provided via flash message. Most of payments has return.pho where these informations are configured and then customer is redirected.
2) no, ita different payment method.

Thank you very much.

also tell me pliz how to display premium services on the ad page?
<?php echo osp_item_promote_manage(); ?>
This doesn't work for me.

@Iskander Bunin
They are shown automatically using hook

the fact is that on my site the automatic display of plugins and custom fields on the ad pages is disabled.
Can you please tell me how to display the information of your plugin using the code?

Well thats essential feature and removing hooks may lead to problems.
These problems must be solved by yourself.
You can search for item_form hooks function in plugin but I am not 100% sure it will work as expected.