Speculating here, but pilots have flight hour requirements for various certifications. Maybe this is a flight that had to happen to log hours but isn’t otherwise necessary so the pilot decided to have some fun.
The Hamburg XFW Airport is used by Airbus to test their new A380 just before delivery. This Christmas flight was the First Flight of this Tail ID so I would guess that it is a new A380 being tested.
The second flight of this A380 looks more like what we usually see here for these kinds of Test flights[1]. Back and forth usually near Hamburg or over Berlin.
[0] https://twitter.com/Airbus/status/940962395463266305
[1] https://www.flightradar24.com/data/aircraft/f-wwae/#fcc5ca7