You may find more info, how to setup Paysera payment gateway in xStore if you open the link below:
https://www.xstore.bg/блог/статия/как-да-настроя-paysera-в-моя-онлайн-магазин-1571751225
Additional information:
* Please place the Paysera logo in a prominent place of your website, such as the footer. The Paysera logo can be downloaded in various formats from HERE.
* Add additional host to your Paysera project URL list, which sometimes is used by xStore system: https://[YOUR_CREATED_NAME].xstore.bg