We should not underrate any club in UEFA Champions League because this teams stands a chance of lifting the UEFA CL title, every team have plans and hopes one day they will br in the final. Who talks about losing when Edin Terzic is not frightened to use his wide variety of competencies to help his side win major games? Dortmund may not have the quality players to play crucial games, but they do have the experience to unite and work together to win games. Borrusia Dortmund leads Group F and has a 50/50 chance of progressing to the next stage of the UEFA Champions League.
Dortmund are currently top of the table in group F with 7 points, then there is PSG in second place with 6 points and then Milan with 5 points and Newcastle with 4 points. Indeed, anything can still happen but if I consider these factors, then it looks like Dortmund still have a chance to qualify for the last 16. Only two matches remain and Dortmund will play against Milan and PSG, in the two remaining matches. At least, although Dortmund maybe lose by PSG, but if Dortmund can still get points in the match against Milan, then it looks like Dortmund will also still finish in the top 2 in this group F. So, although Dortmund did not have good results in the Bundesliga, but it does not mean a total failure for Dormtund in the Champions League too, because in the Champions League all teams have a performance that can be different from bad results in the domestic league.
Yes, if we look at Dortmund's position in group F, indeed they are already in the safe zone by occupying the top position of the three other opponents as you mentioned, honestly I would not fully say that Dortmund is very safe even though they have managed to occupy the top position because obviously the difference from the four teams in group F is very thin, so it is possible that if there is something unwanted in Dortmund's last match such as defeat then obviously the top position will be occupied by another team. Therefore I hope Dortmund will be able to take advantage and maximize their last two matches against PSG and Milan, at least as you said one win between the two matches is still good enough so that they can still have a chance to qualify for the round of 16.
Dortmund run two competitions at once in these two Bundesliga and UCL matches, so of course with this condition they must be able to maximize and fight hard to achieve good results even though only in one league, but it looks like Dortmund might not be too concerned with the Bundesliga and their only focus is UCL, but I hope they will still be able to maximize to play in these two leagues, because of course on the other hand they also have to be able to break the dominance of Bayern Munich in the Bundesliga.