You're right, Haaland still has to prove his performance in the remaining 37 EPL matches. In the next match Manchester City will face Bournemouth and Bournemouth itself is a very weak team IMO. It won't be difficult for Haaland to score at least 1 goal here (if he is played early in the game).
At least Haaland has a good debut in Premier League and it gives him more confidence and energy for his adventure there. If Haaland can move and find space well, creative and smart midfielders of Manchester City can provide him a lot of key passes. So he won't face with lack of key passes to find goals. I think the biggest challenge for Haaland in Manchester City is not how many goals he can score for the club. It is how he will perform in big matches, in important ones that can decide Premier League title and Champions League title.
I think Haaland have got every single attribute to succeed in the premier league If you ask, he's got the pace, movement and extremely good finishing skills, my only fear is if he'll be able to stay fit for majority of the season, because he had some injury worries last year. If that's not not the case, then there's absolutely nothing to be worried about regarding Haaland's chance of making a name for himself in the league, and with a supply line like that Phil Foden, Joao Cancelo and De Bruyne he's bound to score many goals many goals, I have absolutely no doubt!