Read these examples:
. I climbed the hill
. You finished your homework.
. My mum cooked paella yesterday.
. I didn't climb the hill
. You didn't finish your homework.
. My mum didn't cook paella yesterday.
. Did you climb the hill? Yes, I did.
. Did you finish your homework? Yes, I did.
. Did your mum cook paella yesterday? Yes, she did.