Dortmund management must change their attitude if they want to bring the Bundesliga title in the coming seasons because if they continue to sell star players, it is possible that Dortmund will fast for the title for the next 5 seasons. 10 years is quite a long time but Dortmund have always failed to break Bayern Munich's dominance in the Bundesliga.
In the bundesliga, only bayern munich is the most consistent in defending the bundesliga title because other teams are not able to do much because the depth of their squad is relatively dominated by ordinary players but in the depth of the bayern munich squad they are able to present many quality players.
Imagine a team getting back from 1 transfer what they spent in the previous one + benefits. That's what Dortmund is doing to sustain their position while getting new players to train and help them getting the title if possible.
Dortmund are one of the hard numbers in Bundesliga, their problem is having a team like Bayern Munich to ruin their fan, otherwise they would be the first team in the ranking although selling their top players.