Dortmund started the season much better than Bayern Munich. They demolished Frankfurt 5-2 and improved their morale at a very high rate. Haaland was the player of the match that's for sure. He had 2 goals and 3 assists which was a really insane performance from the young lad.
Dortmund are keeping Haaland for this season too but I don't think that they will be able prevent him from leaving next summer.
If Haaland leaves, it will have to be a lot of money for it. I think you might be talking about 200 million euros for example? I can't imagine Dortmund letting him go for less. Don't know until when it is contractually fixed, that will also play a role. PSG not, but maybe City or Barcelona for example? Or Real Madrid?
If he performs like he did last season then I can see it being a world record fee. Real madrid and manchester City are the only ones which could afford him. Barcelona have to many financial problems atm.