Just try to imagine how strong Borussia dortmund is when it doesn't always sell its best players, of course it can win the Bundesliga.
That was already so often written here and the problem is they want to keep this good players but they cant effort the money for it.
If they would have some sponsor like other clubs have they would have for sure good players and would a real opponent for Bayern Munich.
But they can win the team they have now also the German League.