Yes, this could be said to be luck for Porto because Porto managed to take advantage of the opportunity when the visiting team's performance began to weaken in the final minutes of the match and Porto used this situation to break through Arsenal's defense so that Arsenal had to suffer a fairly painful defeat in the first leg, because as far as We know that throughout the match Arsenal were better at controlling the ball in the middle of the field but thanks to the intelligence of the Porto players they were able to keep their defense tight so as not to concede a goal and Porto also tried to create opportunities even though they were a little late but this could be a help for them to jump in. second leg.
This big competition is indeed very challenging for anyone who plays in the Champions League. There is not a single club that underestimates its opponents in any round in the Champions League because sometimes clubs that are not favorites are able to provide surprises, we also don't think that Porto can beat Arsenal because as far as I know Premier League clubs are very strong, therefore Arsenal will avenge their defeat in the second leg because Arsenal performance at home is no longer in doubt in winning the match.
There is one weakness that Arsenal actually has in the UCL, namely that they lack experience. Because they have always failed to qualify for the UCL for a long time. And thanks to Arteta this season Arsenal are in the UCL. It's just that Porto has far more experience in the UCL than Arsenal. But still, in terms of performance, Arsenal is very superior to Porto. So I also believe that in the second leg, the troops built by Arteta will be able to break into Porto's goal with more than 2 goals. And I hope Arsenal can progress to the next stage. Because if Arsenal fails in the round of 16 then it will be quite a big surprise for me. Because Porto is the favorite team and Arsenal should be able to overcome Porto with the performance they are currently having.
Yes, it's true that Arsenal doesn't have much experience playing in the Champions League because the Premier League is quite difficult to get through because the competition is quite tough, in contrast to Porto who always dominate the Portuguese league at the top of the standings so they have more experience in the Champions League and Arsenal themselves can't. underestimate his opponent because after all, Mikel Arteta knows that Porto has better experience, therefore Mikel Arteta wants to take Arsenal to a better level in the Champions League and to be honest, I don't want to see Arsenal eliminated in the round of 16.
I also hope that as you said, the Gunners are able to provide fierce resistance in the second leg because we know Arsenal's strength in the home game, and hopefully this time Arsenal won't make mistakes that cause them to be eliminated in the round of 16 because after all, Porto is not an easy club to be beaten even though playing at home.