Real Madrid is in a bad condition and that was why they played poorly in the first leg. Look at how Brentford was able to hold Arsenal down for a 1-1 draw yesterday, and that made me got confused on which area Madrid didn't get right on that match day. It's nice that Arsenal took advantage of their chances in the first leg with a good goal margin, making it very difficult for Madrid to be hopeful in the second leg.
Arsenal just need to defend so that Real Madrid don't score more than 2 goals, but this goal deficit is far enough that it's hard for Real Madrid to catch up, but don't let Arsenal have the same bad performance against Brentford... it could give Madrid a chance.
Still don't understand Arsenal, why in PL they can't win twice while in CL they can beat big teams with a landslide score, but this is football sometimes full of surprises.