Manchester City are now trying to win the treble of Premier League, Champions League and FA Cup. And it is very difficult to fight for three titles at once and consistently perform well in every match.
I believe they don't mind of winning treble like you told. FA Cup is under their bar and Premier League is not a small title but they won it some times in the last ten years. It is not a terrible season if they lose Premier League to Arsenal. A most important title they want to win is Champions League. They want it not only in this season but also really wanted it in last 10 years and they did not win any title in Champions League. They will concentrate most for it and I don't know whether Pep will stay in Manchester City if they continue to lose it in this season even after having a goal machine Erling Haaland.
Also, Manchester City's performance will deteriorate if any of the team's players, especially Haaland, face injury. However, apart from Haaland, Manchester City have options for every other player. I think Manchester City should now focus on either title. Because Premier League Arsenal are playing very well. On the other hand, Manchester City of the Champions League will face the mighty Bayern Munich in the next match.
Manchester City with and without Haaland will operate with very different formations. Haaland can help them to score goals in his style but generally he requires Manchester City to change their formation a lot. I don't know it is good for them in Champions League or bad for them. Haaland do understand about Bayern Munich with a few years playing in Bundesliga and hopefully he can exploit Bayern Munich defense then bring City to semi finals.