Can you please explain when I have to use each case?
As we know, every noun has a gender, but that gender also has four different variations, depending on where it lands in a sentence. 2. The four cases are: nominative, genitive, dative and accusative a) nominative: "Wer" = Who? ; subject - My mother is an architect. = Meine Mutter is Architektin. - The dog bites the man. = Der Hund beißt den Mann. b) genitive: "Wessen" = Whose or Whom? ; possessive (of...) - des/ eines/ der/ einer - The car of my brother. = Das Auto meines Bruders. - The blouse of the girl. = Die Bluse des Mädchens. c) dative: "Wem" = (to) Whom?; indirect object - We do this with a computer . = Wir machen das mit einem Computer. - indirect object is usually the receiver of the direct object: if you can say for example: the policeman gives the ticket to the driver. d) accusative: "Wen oder Was" ; direct object - der, ein -> den, einen - er -> ihn (= he -> him) - feminine, neuter and plural cases do not change - The dog bites the man. = Der Hund beißt den Mann. - He bites him. = Er beißt ihn.