When Haaland is missing, Manchester City's offense is actually much more harmless.
Haaland is more harmless in this season and in the match with Newcastle United, he shown his harmlessness in many situations and wasted opportunities. One goal scored in the match does not mean Haaland did his job too well.
Yeah, Omar Marmoush is still adapting to the team and it is a big shoe for him to fill whenever Haaland is unavailable, like against Liverpool for example. However, Haaland was fit to play and it was his goal that gave City the win against Spurs, big win for them as they fight for top four. By the way, sorry to Arsenal fans, you guys are no longer in any title race with Liverpool, it is officially over, the league is Liverpool's.
Marmoush is an attacking player with different style than Haaland, those two players can support each other well. It can be a classic combination between a striker and a forward with Marmoush can be used at the forward position and Haaland at a striker position in Manchester City. Manchester City have very flexible tactical operations but I believe that in the center or two swings of their attacking system, Marmoush with his skillset can support Haaland very well.
He in fact needs more time to adapt to Manchester City tactics and his new teammates. A next season will be promising for a combination of Haaland and Marmoush.