Einen and or Einem?
Ich habe einen Apfel mit einem Mann. I Don't understand Why einem is used, because I was taught that einen means a or an and then suddenly Duolingo starts teaching me that einem can also mean a or an. Is einem the formal a or an, do you think/know?
It's dative. German has a more complicated case system than English. The dative form is used to indicate the indirect object of a sentence, or after certain prepositions. In your case, Mann comes after mit, which is one of the prepositions you always use dative after.