Haaland now has 19 goals across all competitions after his double, as Riyad Mahrez, Julian Alvarez and an own goal by Davit Khocholava ensured our 100% winning record in Group G continued at the Etihad Stadium.
Grealish, who was awarded the Player of the Match award, played a huge part in the build up to multiple goals under the floodlights and was a constant nuisance for the Copenhagen defence.
The Englishman had nothing but praise for Haaland's astounding start to life at City.
"Do you know what, it’s unbelievable honestly," he said. I’ve never experienced anything like it in my life. I was just laughing, like how?!
"He’s always there. It’s a pleasure to play with him. Their goalkeeper said to me after one of his goals, he’s not human! I was like I know.
"He’s so humble, he’s great around the place, that's God's honest truth. Hopefully he can carry this on and fire us to glory."
Grealish was at the heart of everything good for Pep Guardiola's men, having 92 touches of the ball in a wonderful display in matchday three of Group G.
The winger was happy with his performance and is now looking to add goals to his name.
"Yeah I loved it. Obviously playing in the Champions League at Etihad is a great feeling, Three wins out of three in the group and at the top, it was a great night!
"I’m loving it at the moment. My last three or four games I feel back to myself. I’m playing with freedom and confidence.
"Hopefully I could have got on the scoresheet and I was desperate, especially in the second half, but it’s all about enjoying it and winning and that's what I'm doing at the moment.
"It’s just when the luck is not with you. I’m going through one of them patches where nothing is falling for me. I’ve played a lot recently so I'm thankful to the manager.
"I’m playing with a smile on my face and really settling in here now."