I am new to learning German on Duolingo and am really only having trouble understanding when to use nominative and accusative.
I can't seem to find anything that helps me understand, could someone here help?
The nominative is the subject, or the thing that is doing the action that the verb indicates.
Ex: Der Mann isst einen Apfel. "Der Mann" is the subject and falls into the nominative.
The accusative is the object, or the thing that is receiving the action of the subject.
In that same sentence "einen Apfel" is an object and accusative and the indefinite article is changed accordlingly.
So use the nominative for anything used like "Der Mann" and the accusative for anything used like "einen Apfel."
In short: Nominative - subject, accusative - object
I hope that helps!