Even before several of their players were injured and underperforming, Manchester United's previous performance cannot be compared to that of Bayern Munich, and they are far superior to them and will finish ahead of them in the group stage. Manchester United still has a chance to finish second in the group because they have four more matches to play, but I doubt they can beat Bayern Munich in their second leg clash. If they lose or draw a point with Bayern Munich, they will be disqualified from finishing first, and Bayern Munich will almost certainly win their remaining four matches.
I think MU's chances of finishing in second place in the group will be very difficult, because Manchester United's performance itself is unstable or inconsistent. I prefer Galatasaray, in the domestic league they are quite impressive with the 8 matches they have played, the 7 wins they have achieved and so far they have never lost. On the 24th Galatasaray will play against Bayern Munich with full support from the crowd, I am sure Galatasaray will get points at home to maintain the points position in the group