Dortmund's performance was not very good, I thought they would score much easier and win with a few goals difference. Even though they dominated the game, they could only score one goal. It might be enough to get 3 points but I think they could have played better. Next is to win the Champions League match 
I thought in yesterday match Dortmund would at least get 2 scores but it turned out not to be what I thought because as you said Dortmund did not appear perfect while Bremen was not very strong team but Dortmund looked like they were having difficulty in that match but luck came after Julian Brandt managed to get 1 score for victory. TBH, previously I was worried that Dortmund would not be able to win that match because they almost not score and I thought that if yesterday match failed to win, Dortmund would still be inconsistent, but it turns out that Dortmund has really started to become very stable.Dortmund has the opportunity to be at the top of the standings, but when Leverkusen, Stuttgart and Bayern Munich have played their eighth match, the standings will change and will again put Dortmund below the three teams if the three of them succeed in winning over their opponents.