What would Adolf Hitler do to me?

Nazis didn't generally concern themselves too much with blacks because there weren't that many in Germany at the time and they just thought of them as inferior not as a threat like they did with the Jews. However they wouldn't have tolerated the disrespect or the race mixing and likely arrested you and sent you to a camp or prison for the behaviour you describe. A black person in Germany who lay low and didn't cause trouble though likely wouldn't have been bothered. In fact, some of the black American athletes who came to Germany for the Olympics during the Nazi regime were treated better in Germany than they were in the USA - they could drink from the same water fountains, sit at the same lunch tables, etc, as everybody else.