Bayern Munich winning the first leg is what I don't understand and secondly I don't think Arsenal will be so stupid allowing Bayern Munich win at the Emirate stadium. Concerning the second leg I can't predict but if the goal difference is much during the first leg then Arsenal will definitely win the game.
From my opinion predicting the match is difficult but let's not forget the strength of both teams this season and Arsenal has been playing effortlessly, watching yesterday match also show the strength of Arsenal this season so I don't think Bayern Munich will win so easily or rather I don't think Bayern can defeat Arsenal.
in the first leg what might happen is a small difference in score. it could be 1-0 or 2-1 in favor of the host.
Arsenal is not a weak team, but facing Munich, which is also a strong team, is like a final match. However, both teams have enough abilities to beat each other. but there will only be 1 who passes.
This is a difficult match, just like the Madrid vs City match.