I don't think Manchester United have any chance of qualifying from this group anymore because their next game is Bayern Munich,and there is no way United can win Munich,if they cannot get a win against Galatasary or Copenhagen,then their hope is already lost.
There is always a chance for a surprise thing in football. We already saw many surprises happened in the previous seasons. So, it is not impossible if Man United can surprise us by defeating Bayern Munich and qualify for the next round. We know that Bayern Munich status is qualified for the next round, the last match isn't a very important match for them. So, Bayern Munich actually has no motivation anymore to play all out in the last match. This can be the chance for Man United to steal points.
-snip- is it possible for Man United to beat Munich, which is said to be the strongest club in the UCL, that is clearly impossible unless Munich underestimates Man United too much and plays their second tier players to help make things easier.
I think it is not impossible although it seems a very small chance to beat Bayern Munich. However, if Bayern Munich uses their substituted players (second tier players) for the last match, I'm sure Man United has a chance to beat them. Moreover, the last match won't impact anything for Bayern Munich, they probably don't want to push themselves so hard in the last match.