Dortmund needs to look for a replacement for Haaland because it is very likely that Raiola will find him a new club this winter. Of course one should not forget about the defense because indeed in Dortmund there have been quite big problems with it lately.
It would be really good for Dortmund to start doing some research about some strikers already now. Because Erling Haaland is very likely to leave the team in next summer. I don't believe that some club can manage to sign him in January already but I'm very sure about the summer transfer window. Clubs like Real Madrid, Manchester City, PSG and Manchester United are already thinking seriously of signing him. If Dortmund can't fill his place with a solid striker, then they can have bigger problems in the next season I assume.
Sooner or later haaland will certainly leave dortmund, especially from several sources that say that the release clause that haalaand has is not too high for big european teams, currently haalaand still has a contract until 2024 with dortmund but the release clause is only around 75 million euros certainly makes it possible for haalaand to move to another club, I think in the near future for sure haalaand will leave and it's better now dortmund look for players who can indeed replace haalaand position in their front line, and reportedly dortmund have targeted two players who projected to replace Haalaand position, namely Sebastien Haller from Ajax Amsterdam and Patrik Schick from Bayer Leverkusen.