2)Could Ivan speek three languages when he was five?Ivan couldn't speek three languages when he was five.
3)Could we help you with that?
we couldn't help you with that.
4)Can they take us to the restaurant?
they can't take us to the restaurant.
5)Could you come with us?
you couldn't come with us.
6)Can Marta drive a car?
Marta can't drive a car.