I’ve received the answer:
Thank you for reaching out to us. We are here to assist you. All strings used in our plugin are translatable and we provide full compatibility with?WPML. Unlike the WPML plugin, the Polylang plugin handles translation with XML files. We are sorry to let you know that our plugin currently does not support it. The compatibility with Polylang is already in our development pipeline and since it requires some development efforts and internal changes we cannot commit to it at this moment.
I’m closing the thread.