Of course those were really hard times for Dortmund. But it seems like they have learned their lesson from that as we don't see such unnecessary transfers. They are only focused on reasonable transfers in which they can make a big profit. Sometimes things don't go exactly as they imagine as well of course.
Dortmund is the most discussed team in the Bundesliga and the same as Bayern Munich.
These two teams dominate the Bundesliga the most because they always compete fiercely in matches and player transfers when preparing teams for the upcoming season.
In this transfer season, I don't see anything special being done by Dortmund, but it looks like there are several players who are targeted to strengthen Dortmund in the summer.
If I compare between Bayern Munich and Dortmund, I think I'm more interested in Dortmund. Because after all, Bayern Munich only has a record as a club that really dominates the Bundesliga by winning consecutive titles. But in fact, Bayern Munich also quite often get great players from Dortmund. Also about Dortmund, even though Dortmund often sell key players and star players, but Dortmund has always managed to build a team well. The proof is, Dortmund has always managed to challenge Bayern Munich in the title race and because of that, I think Dortmund is a very unique team. Because no team can produce great players every season like Dortmund and also be willing to sell them, it's like a tradition that only Dortmund seems to have.