Researching the history of a radio operator

[Nioldur]

Hi all,

I hope this is the right place to ask this. My Grandfather was a radio operator in the Luftwaffe and part of a bomber crew. And unfortunately that is about all I know about him, since due to my parents divorce and also my grandparents sailing around the world and not being at home I never got to know my grandfather all that well and have no contact to my father's side of the family.
I want to know more though and start researching his history within the Luftwaffe and I am looking for hints on how to start. If possible I would like to start with online resources but visiting the archives in Freiburg would also be possible.
If by chance some of the knowledgeable people on this board already have some information about him that would be perfect of course. His name was Christoph Vogelsang

Thanks all!