So what are the correct forms of address?
When addressing a woman, write “Mrs” or the more up-to-date “Ms” (sounds like “miz”). Use “Miss” for a girl under 18. When addressing a man, write “Mr“.
There’s a difference here between British and American English. In British English we don’t need a full stop (or period). In American English we do. So in American English we write: Mr. Mrs. Ms. Miss is not an abbreviation (Abkürzung) so there’s no full stop (or period)!
Oh, before I forget, in Germany we may greet someone with a doctor title as follows: “Guten Tag, Herr Dr. Meyer”. In English we would say: “Good afternoon Dr. Meyer”. We do not say “Mr Dr”!