Dortmund was a good team but currently their performance is going bad. After Halland's departure, they could not add any player to fill Halland's place in their team. In view of which, Dortmund have some problems in attack.
Dortmund is one of the best teams and Erling Haaland's departure should not be the reason for his defeat in several matches, even though in his last match Dortmund lost and could not lead the top of the standings but there is still hope for Dortmund to get into the top 3, although it will be very difficult to do so and it requires a lot of effort.
After Erling Haaland left for Man City, it is now Jude Bellingham's turn who is rumored to be going to another European club, but it is not certain which club he will sign the contract with. Apart from that, Dortmund can't just keep quiet, they are far from good this season, being in 6th place in the standings is a bad result that they must fix immediately. Targeting new players in the transfer market is one way to deal with the team's current performance, it seems that coach Edin Terzić seems to have thought about this.
That's how the team if too focused on their business, it can backfire on themselves. I won't say that the business they have been doing is wrong, because in football, business is also one of the supporting factors for their finances. However, they should be able to distinguish and sort more what they can do and what they can't do (I mean excessively). When they sell some of their important players in the team, I think it's a little bit over the top and they don't think about their future with the club.