Probably German citizens knew that Jews and other minorities were doing hard labour in concentration camps, but were they aware of extermination camps like Auschwitz or Treblinka?
This is a frequently asked question and you can find various answers to it in the faq under holocaust section. Here’s one answer though: https://www.reddit.com/r/AskHistorians/comments/3mnglz/did_the_germans_who_lived_near_concentration/?utm_source=share&utm_medium=ios_app&utm_name=iossmf
I have previously found relevant answers by /u/commiespaceinvader and /u/estherke in To what extent was Hitler able to keep the brutality of the concentration camps secret from the Allies and the German people?
See also At what point did the existence of Nazi concentration camps become public knowledge and what was the public response? answered by /u/PeculiarLeah.