Milan have won two of their first three games under coach Marco Giampaolo.
Donnarumma said: "We're a beautiful group. With a new Coach it's normal to have some difficulty at the beginning, but we're working well.
“We've picked up two wins from three, not playing very well, but winning helps us win more and slowly we're getting to grips with our game.
“A derby goes over everything else, it's a game that prepares itself and gives out a lot of energy and emotion. Playing the derby is a unique satisfaction.
“Samir [Handanovic] is a very good lad and a great goalkeeper, I like how he attacks the ball, plus we know all his other qualities.
“With D'Ambrosio I have a beautiful relationship, he's my compatriot and he also lives near me. I'll surely cross him."