Manchester United's relationship with Ronaldo has ended. So I'd say it's better not to discuss it.
Both Barcelona and Manchester United are playing well. Both Barcelona and Manchester United won yesterday's match. And both the teams were able to dominate and win. So it becomes more difficult for me to predict which team will win.
Lewandowski and Dembele have been performing consistently well. And Barcelona's main strength is their midfield. Barcelona's performances are now very stable due to the consistently good performances of the midfielders. But their defense is still weak. I would say, if against Manchester United, Barcelona's defenders can play well, then Barcelona has a chance to win.
Barcelona's defense has actually been very strong so far, but that's in La Liga. Meanwhile Barcelona look very different in Europe so I don't expect a win from them over two legs against Manchester United. Jules Koundé, Ronald Araújo, Andreas Christensen and Alejandro Balde are in good form so far. They look strong at guarding Barcelona's defense, but I think Manchester United has way of making Barcelona's defense work hard.
The two teams have different playing styles, and I think Barcelona will still try to dominate the match in their trademark style and that will allow them to manage the tempo of the game. Barcelona successfully won the Super Cup from Real Madrid, while they also successfully advanced to the semifinals of the Copa Del Rey, and Barcelona is the leader in La Liga. There is high enthusiasm from this Spanish team, so Manchester United's wariness of Barcelona will certainly increase.