Galatasaray will have to work hard to overturn a three-goal deficit if they want to qualify, this mission is certainly very difficult for them because AZ Alkmaar have no pressure in this game, they only need a draw or a 2-0 defeat to qualify for the last 16. AZ Alkmaar will be looking for a safe spot after a big win in the first leg, they just need to add strength in the defensive area and occasionally counter-attack to put pressure on Galatasaray. Galatasaray may be able to win this game, but their chances of qualifying are very slim.
What you said makes sense because AZ Alkmaar themselves are already aware that they do not need to pressure Galatasaray with more attacks in this match so AZ Alkmaar will focus more on defending and counterattacking tactics when possible. Because AZ Alkmaar can still qualify more comfortably for the next round even if they lose 2-0 in this match, especially if the match is a draw, of course it will be very beneficial for AZ Alkmaar. But I am not so sure that their match will end in a draw because Galatasaray will definitely launch more attacks in this match.