It would be unreasonable to expect anything like that from Sebastian Haller. If anything they are trying to make him one of the premier strikers. After that, they are going to sell him again like they always do for a substantial amount of money.
And I think they obviously had problems with the defensive lineup. However, they also could not score enough goals as their main striker Erling Haaland was injured for quite a long time in the last season. I hope that this time they don’t have any problems like that and they will be able to play attacking football.
Haven't seen Haller play since at West ham but yeah Haaland has the unique play style and movement so certainly will be missing out on those I guess. Haller is a good player and has improved a lot while his career at Ajax but I still think that he won't be much impactful as Haaland was. I also think he will be sold later onwards if they find a young potential player. But still Haller is not a bad signings, just made to patch things up for the moment.