Haaland tapped in his second of the evening and 12th of the season in all competitions shortly after, before Ruben Dias added a late fourth.
De Bruyne, who was awarded the Man of the Match award in Spain, was happy with Haaland's perfect start in the Champions League for City.
"I try to do my job and make the right movements and create the most chances I can," admitted the skipper.
"I know one way or another Erling [Haaland] will be there. At the moment he’s scoring the goals. For him it’s a perfect start.
"I think the way he has adapted to us is really good but obviously, outside of the goalscoring there’s another part of the game and that is more tough to adapt to.
"It makes it exciting if he can adapt to see the outcome. If you score that much you can get away with things. If he keeps on scoring then we know it's a positive for us."
City are top of Group G after the convincing victory and the Belgian midfielder believes that with the display and victory, City have laid down a marker for the remainder of the group stage.
"Obviously it’s a very nice stadium to come to with the loud fans. It’s the first away game and it is very important, you have to set the tone and I think we did that today.
"It’s nice to start the group with a win.