First of all let me say thank you to all of you. I assumed that my topic had to be approved first and then I will be noticed but things are going the other way round.
I have answered a few question in the answers already. In the meantime I know a little bit more about this two losses.
The two P-39 Airacobras were of the type P39Q-21 (at least the one with SN 443914). And indeed they belong to GC II/9 Auvergne. I got a report from a Swiss historian where this SN is mentioned, it is a report issued by military command. Searching the web I found a french magazine (Aero Journal, No 39) with a description of GC II/9 Auvergne. There is even a photo with exactly that airplane [big luck].
It belongs to the 1ère Escadrille of GC II/9 and was taken around March 1945. At that time GC II/9 was stationed at La Vallon in the southern part of France not far from the Côte d'Azur
(see photo)
Regarding my model there are two questions: first the color of the spinner? Usually the P39 of GC II/9 had their spinners painted yellow but on the photo the spinner is quite dark so it might also be red.
Second, the aircraft dosen't cary a big number on the front of the fuselage as a lot of the French fighters did. Either it is a bad photo or it really has no number, at least not when the picture was taken.
Even with these two questions open it would be possible for me to build that particular aircraft as a model.
Now let's find all that information about the second P39 too.