Bayern Munich failed to beat Copenhagen at home just because they had already qualified for the last 16 of the Uefa Champions League. I bet you Bayern Munich will want to beat Manchester United at Old Trafford even if they had qualified for the next round of the Champions League.
Bayern Munich will win Manchester united if they had their qualification at stake, considering their present form, they have a better form than that of Manchester united and on a normal day they will win Manchester united with a good goal margin with little or almost no stress due to Manchester's current form.
In this match, I doubt if that will be the case because Firstly Manchester united is considered to have something at stake meanwhile Bayern Munich almost has none, checking back at the last time both teams met in the UCL the game ended in a draw, although I would possibly say Manchester united was in AA better form than they are now and their form most recently has been so inconsistent and almost unpredictable so I can't tell, probably the consciousness of what's possibly at stake could likely get them to perform better and Bayern may use their rotational players to preserve their key players because they have almost not at stake so this may be the advantage Manchester united may have, so we can't be too certain at this moment who will win by the end of the match.
Even though Bayern Munich does not have anything to play for since they qualified for the Uefa Champions League last 16, Bayern Munich would like to beat Manchester United to protect their pride of not losing to a big side like Manchester United. With the current form of Manchester United, they will find it difficult to beat Bayern Munich.