There is no guaranteed unless it is mathematically guaranteed. Bayern guaranteed that they will win it this year, and Dortmund guaranteed that they will be second.
No guarantee at beginning and they have achieved good results from their training, efforts. Bayern again beat Dortmund to take Bundesliga trophy. In the summer, Bayern will have to sit back and think of replacements and future stalrategic plan for the club. They will not buy Haaland, and they might lose Lewandowsky as a free transfer. Who will replace Lewy in Munich? Some key players of Bayern are old and soon need to be replaced. Mueller, Neuer for example.
I didn't know the Dortmund deal, if City gets him 100% guaranteed not fake news, that's one of the biggest news of all summer transfer window, even before summer came.
It is big news (if it is true) for City and Premier League but not a good news for Dortmund or Bundesliga. They will lose one of their best players not only in last seasons but alos in a long future ahead. Because Haaland is too young and if his body is good, avoid injuries he will have about 10 years and more for his career.