My best guess for the text below BÜLOW is "Deutsche Flugzeug Werke (newline) Leipzig".
[![enter image description here][1]][1]


Having three pairs of struts on each wing would make it a [DFW B.I][2], C.I or C.II, as later models only had two pairs of them.

[![http://flyingmachines.ru/Site2/Crafts/Craft25582.htm][3]][3]

The small gap between the wings matches the photo too.

While some [prototypes got a machine gun][4], the standard version of the DFW B.I was unarmed.

According to the book "German Aircraft of the First World War" (Peter Gray & Owen Thetford) the only difference between the C.I and C.II version is the position of the pilot (C.I: pilot in rear seat). Another [source][5] mentions the change of the machine gun from Parabellum to a synchronized one. A synchronization gear only makes sense attached to a fixed machine gun below the upper wing.

With a gun over the upper wing and assuming that Bülow is sitting in the pilot's seat, I'd say that the airplane is a DFW C.I.


  [1]: https://i.sstatic.net/zhad0.png
  [2]: https://en.wikipedia.org/wiki/DFW_B.I
  [3]: https://i.sstatic.net/tEQsTm.png
  [4]: https://de.wikipedia.org/wiki/DFW_B-Typen#Weiterentwicklung
  [5]: http://www.airwar.ru/enc/other1/dfwc1.html