Haaland won and converted a penalty for the first goal, before latching onto a Kevin De Bruyne through pass to score his and City's second of the game.
"All the team were amazing, but for Erling to score the first two goals is good for him and for us," Guardiola said post-game to reporters.
"He is a threat for us now, but he is not going to solve all our problems.
"He will add something to our team. But if we just rely on him, we will be making a mistake.
"I'm so happy for him. Two goals, the debate is over. He scored goals in Salzburg, Dortmund, so hope he can do it here."