Dear Adriano,
Thank you very much for your answer. If Erich Rudorffer and Walter Nowotny never met, this photo must be a photomontage.
Of course, they may not have been friends, but they may have actually met.
Unfortunately, I have no photos showing Friedrich Rupp, Walter Nowotny and Horst Hannig together, so I don't really know whether they met or not. All I know is that Friedrich Rupp and Hans-Ekkehard Bob were friends and that they had actually gone to school together.
By the way, where are you from?