Lazio might be able to win the match and qualify if they can score early and also not concede in the next match. Scoring 2 goals is actually possible for Lazio if they can really dominate and destroy their opponent's mentality. But we have seen the results of the first leg, the opponent will not be easy to beat.
I think United's situation is more complicated. To be honest, I was also surprised they got 2 goals in the first leg. But in the second leg, maybe both teams will play tightly. And I don't think there will be many goals. It could be just one goal that decides, but I hope the match will be interesting.
It's going to be a difficult game for Lazio. I've watched Bodo/Glimt play and they are really good. Lazio will be playing at home which should give them an advantage but I doubt if they will be able to cancel the two goals.
About the Manchester United match, I noticed something in the second leg against Real Sociedad. United were able to identify and mark out Real Sociedad's main man, Oyarzabal, and by so doing they were able to keep the visitor's quiet. Maybe Amorim is going to deploy same tactics against Lyon. But again, United need to score goals and their frontline have not been prolific but I just hope they all step up and bring their a-game into the match.