Hello Holck
I have that his stamm-regiment was IR 152 and that he received the pilots badge on an un-specific date during 1913.
He was promoted to Oblt on 27 Jan 1915 (a perfect day..

)
Kasta Trier, 31 and Sosta 1 were "all" actually the
same unit which had been re-named a couple of times...The first name of this unit was Kampfstaffel Cöln...
Gunnar