My girlfriend is in the process of learning german grammar at the moment, and she struggles a little with learning when to use which case. For Nominativ and Genitiv, we found simple rules when to use each of them.
Nominativ is used for the "subject" of the sentence. The Nominativ is the person or object which executes the action described in the verb.
Genitiv is used to express posession or belonging. Whenever an english translation could use "of the", it's Genitiv.
I am struggling to find similar examples for Dativ and Genitiv. Wikipedia states that "the Dativ describes the person, to whom an action is directed towards."
However, this seems a little counter-intuitive, if I use the example:
Ich werfe den Ball auf den Mann.
Both "den Ball" and "den Mann" are Akkusativ, even though knowing the above definition one could claim that "der Mann" is the person to whom an action is directed towards.
As such, I would like to ask if there are any rules how to tell apart Dativ and Akkusativ?