City have never won Europe's elite club competition and were knocked out by eventual champions Real Madrid at the semi-final stage last season, having finished runners-up to Chelsea in the 2020-21 campaign.
Speaking to reporters before Dortmund's visit to the Etihad Stadium on Wednesday, Gundogan said Haaland's brilliant start to his career in England can translate to success in Europe.
"We hope for it. This year having a proper number nine is going to help us a lot," Gundogan said. "We will see and the Champions League is an incredible thing to achieve.
"It's never easy to play in this competition and sometimes little details can decide the outcome."
Haaland has hit the ground running since joining City in the close season with 12 goals in all competitions so far, including two on his European debut for City as they beat Sevilla 4-0 in their first game to sit top of Group G.
"The numbers they speak for themselves. I think the club has signed an incredible player," Gundogan added. "He's done well on the pitch, but his character, determination and attitude off it (has also been impressive) from such a young boy.
"He's very mature and his future is very bright. We're both really looking forward to the game against our old club."
City manager Pep Guardiola said another former Dortmund player, Manuel Akanji, was in contention to play in the game.
"They (Dortmund) know these players (Haaland and Akanji) more than I know Dortmund players, that's for sure," Guardiola said. "They were there a few years. They can benefit.
"We'll see tomorrow if it's an advantage. But they know the Dortmund players too."
Guardiola said Aymeric Laporte trained for the first time following knee surgery while fellow defender Kyle Walker missed the session.
