How to register a previously-owned SG Firewall with new owner?

I have purchased a previously-owned Sophos XG-115 firewall. The device is still registered to the original owner. There are also several active (i.e., not-yet-expired) subscriptions installed on this device. Questions:

  1. What is the proper procedure to de-register the device from the previous owner and register it to the new owner of the device?
  2. Is it possible to transfer active subscriptions from the previous owner to the new owner?

Thank you.