The first thing the nazis did, was purge the bureaucracy. Taking away guns was no concern, at all.
Privately owned guns played no significant role in the nazis’ rise to or hold on power. Anything else is simply marketing by american gun sellers.
Some of their victims hid, refused to give up their arms, and fought back. They didn’t survive.
About 10-15,000 jewish germans survived the holocaust by going underground in Germany. They were colloquially called U-Boote or Illegale. Of course, that has nothing to do with guns. Guns were, after all, handed out to any able-bodied male.
If guns were the answer to dealing with fascism and authoritarianism, germany never would have had the holocaust.
That is only partly true. Germans are only a small fraction of holocaust victims (<5%). The victims overwhelmingly came from eastern Europe, particularly Poland and the Soviet Union. The holocaust happened in the wake of the advancing Wehrmacht. A more far-sighted response to german war preparations would have made a difference. A lesson one must bear in mind in today’s world.