When Arsenal was drawn against FC Porto in the round of 16 of the UEFA Champions League, I expected Arsenal to win against FC Porto but with the recent performance of Arsenal, I'm not sure if Arsenal could be able to beat FC Porto. If FC Porto can play well in their home, I believe they will beat Arsenal.
I do not understand what you mean. In fact, the round of 16 matches will start in February and you have already said that Arsenal have achieved a draw against Porto. You don't seem to really understand or you didn't check it. I think Arsenal's opponent in the round of 16 cannot be underestimated because Porto will be the host in the first leg and if the result of the first leg can be won by Porto, it is likely that the second leg will be quite difficult for Arsenal.
Arsenal certainly performed quite impressively in the Champions League this season, Arsenal were even able to qualify as group winners, which of course means they will be very favorites in the match against Porto. Arteta must be able to take Arsenal to go far this season because they have quite strong strength this season and they only need to improve their front line in this transfer market.