If Galatasaray can get points against Bayern Munich, they will have a great advantage to finish the group in second place. Of course, let's be frank, I think Bayern Munich is the favorite of the group and these matches. Manchester will aim for 6 points in the two matches they will play against Copenhagen. If Galatasaray cannot get points from Bayern in two matches, the match they will play with Manchester United in Istanbul will become much more important.
I don't see that happening, Galatasaray doesn't stand a chance and can never stand a chance with Munich, the fact they they were lucky with Manchester united doesn't give them the chance to face Munich and secure a win regardless that Munich is not at home, not at all, on a good day if they had met with an informed united they don't stand a chance let alone Munich in this current form.
Placing these two teams H2H you will see that they are not at all of equal strength even in personalities we have the like of Kane and the rest to deliver Munich but I'm yet to see any person in Galatasaray who can contend those in Munich, although Galatasaray may be on good morale now because they may still be in the ecstasy of the win they just had over Manchester united but then if they manage to make it to the knock out stage it will be a good achievement for team amidst the big contenders they have on their group.