GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
That's most likely a MG151/15, which was installed on Do17s during the BoB.
They did install MG151/20s on some Do17s, but the barrel looks to be the 15mm variant in the photo.
Warthunder is just loaded with fantasy bullsh!t, so always take anything posted there with a grain of salt.