In my opinion, Galatasaray is not a worthy opponent for Bayern Munich, it's just that Manchester United was really bad against them. Bayern Munich is the favorite in that match, in fact I really believe that they are one of the favorites for the title this season. It is true that Bayern Munich should not underestimate Galatasaray, but on paper Galatasaray will not win that match without really getting lucky.
Galatasaray, who is playing at home, certainly deserves to be watched out for because they also have the desire to win points. But when quality and experience become a comparison, then I have no hesitation in saying that Bayern Munich will win that match easily.
The difference in terms of their strength is too far but indeed in real football things like this can be for Galatasaray to try to hold back with a draw.
Now we just need to see what scheme they will show in this match. Trying to keep up with the game from Bayern I don't think this will be too good for Galatasaray but waiting with the parking bus could also be complicated for them so they need to think carefully about what they should do in this match.