It is certain that Dortmund will be the winner at the end of the season. From a long time ago I have said that Bayern Munich's position is less profitable because they have to face Leipzig in the remaining matches. Meanwhile, Dortmund played against teams that had almost no influence at all. On the other hand, we can see that Leipzig is a team that cannot be underestimated. In third place in the standings, it is certain that Marco Rose's children have an extraordinary threat and will not let the match become easy for Bayern Munich.
Now there is only one match left for Dortmund, namely against Mainz, if Dortmund manages to get full points over Mainz then the title will come to him. I'm sure Dortmund will give their all for this match and on the other hand, it won't be a difficult match for Dortmund.
It is not certain that Dortmund will win Mainz. We have seen many shocking things happening in football. They need to be focused and don't get ahead of themselves, they've not won it yet.
Dortmund should have been comfortably at the top of the table by now, in fact they might have won the league by now if they did not blow the other opportunities they had in the league. So now they should not make any further mistake. Just win this match and the league is theirs.