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.
The player that was targeted by Dortmund was Edson Alvarez, a midfielder from Ajax Amsterdam. However, the plan to recruit Edson Alvarez failed because there was no agreement on the price desired by Ajax Amsterdam. Ajax Amsterdam has set a selling price for Edson Alvarez of 40 million euros, this is a high enough price for Dortmund and Ajax cannot be negotiated either.
Besides Edson Alvarez, Dortmund are also eyeing Sheffield United's young striker, Daniel Jebbison. This 20 year old young player is also a target for Juventus, Dortmund still have to compete for Daniel Jebbison to get this talented young player.