Yeah Bayern Munich will play with a bad defense since Neuer, Upamecano, De Ligt, and Guerreiro are injured, this will make Galatasaray able to score against Bayern Munich. It also depend on Bayern Munich striker, will they score more goals than Galatasaray or not.
Honestly I doubt Galatasaray can beat Bayern Munich, I think the biggest possibility would be draw.
Yes I think it will be difficult for Galatasaray to beat Bayern Munich in that match even though the match will take place at Galatasaray's home ground. The good capital shown by Galatasaray in the domestic league and the last match in the Champions League will give hope of a chance to beat them, especially if Bayern Munich's defense is not strengthened by players who have good abilities due to injuries.
Tuchel must try a solid defensive system in this match, away games will be much more difficult because Galatasaray will definitely be aiming for full points in front of their own crowd. A draw would be enough for Bayern Munich, if Galatasaray played more pressingly like in the previous match against Manchester United.