Now, Chelsea already leads with 2 goals, the aggregate 2-1 for Chelsea.

I am surprised that Chelsea played well so far, they seem to be more motivated to qualify for the next stage in UCL. They dominate the match and they become very offensive. If they can keep this good game, no doubt Chelsea to play in the next round. They are playing at home now, they have a bigger chance to qualify.
By the way, Chelsea already made 12 shot attempts, 4 shots on target. While Dortmund only made 5 shot attempts, only 1 shot on target. It is very clear that Chelsea is more superior in this match.
Despite playing so well, They haven't yet killed off the game. 1 Goal from Borussia Dortmund and they are off to Extra time and possible penalties. I guess Graham Potter will stay a little longer after tonight's performance, but we all know he is not completely secure