I've seen so many documentaries and read so many witness accounts from Germans alive during the times of the Holocaust that say that for the most part the German public was not aware of the Holocaust and it's only something they learnt about after the fact, this is also backed up by testimony given by German soldiers and officers at Nuremberg in where they said it was a fairly closely guarded secret that was only known by higher ups and people that were actually involved one way or another, but largely it wasn't actually common knowledge.
I don't know how true this is but apparently Hitler forbade it being a topic of conversation in his presence and apparently he was very 'hands off' when it came to the final solution, it was something he was aware was happening but he didn't particularly like to talk about it or even really acknowledge.
Having said that, I've always assumed that like the conspiracies surrounding the Apollo Space Program, far too many people would have to of been involved for it to be a secret, and given how many people of all different ethnicities died as part of the Holocaust I really can't see how it couldn't have been public knowledge, it's not like we're talking about a small government-run project that employed only a few hundred people here, we talking about millions of people being exterminated.
Not to discourage further discussion, as there is always more to be said, but you may be interested in these previous questions: Did the Germans who lived near concentration camps really not know that they were there? (by u/kieslowskifan); To what extent was the German population aware of the atrocities of the Holocaust? (by u/commiespaceinvader); How did it become common knowledge that Nazi German was killing it’s population? (by u/estherke); Did Hitler know about the Holocaust? (by u/commiespaceinvader); and When did Americans, and the rest of the world, discover the atrocities towards Jewish folk during World War 2? Was it known about prior to our entry to the war, or only discovered after reaching Germany and happening upon it during the campaign? (by u/commiespaceinvader).
Although the linked discussions go into far more detail than I can, the TL:DR is that yes: the average citizen of Nazi German would have known. The T4 Program (the “eunthanasia” of people living with disabilities, and a precursor to the Holocaust), was public knowledge, and the outrage that followed lead to widespread protests in Germany. The deportation of Jews from Germany to the camps was no secret, as people witnessed their neighbours and co-workers being rounded up and never returning. It’s important to keep in mind that the vast majority of the actual killings of the Holocaust were committed outside of Germany, with most deaths occurring largely within occupied Poland and the Soviet Union. While the local populations definitely knew what was going on, it wasn’t uncommon for soldiers and members of the *Einsatzgruppen (*death squads sent to Poland and the Soviet Union), to write back to their families about what they had witnessed. All this is to say- most everyday German’s would have known that something was happening, although it is hard to gauge if there was a widespread understanding of the extent of the atrocities.
Another interesting note is that the Allies also knew about the Holocaust as it was happening. Intelligence reports (for example The Einsatzgruppen Situational Reports USSR), were intercepted and decoded which detailed the killings very clearly. Furthermore, spies from the Armia Krajowa (The Polish Resistance), broke into Auschwitz and smuggled out reports of the camps operation, trying to raise awareness in both the UK and the USA.