Strange bright objects seems to merge over Piotrków, Poland

Submitting on behalf of my friend, who's also a trainee pilot and his partner. Weird wedge/triangular object spotted by his partner first, who thought there's something burning, then thought its a moon, but excluded that possibility after observing moon on a different spot in the sky on December 7, 2020. 


The object hovered for a long time, pulsating slightly. At some point blinked and disappeared then reappeared again with its twin (actually, there were two of them at the same time for a brief moment) then the two objects seems to merge before flying away. Mufon.