By Jamie Spencer Mikel Arteta has vowed that Arsenal will at least learn from the manner of defeat in the club’s first Champions League knockout game in seven years, having been beaten by Porto. The Gunners enjoyed the lion’s share of possession against the Portuguese giants on their own pitch and yet didn’t muster a single shot on target – the first time that has happened in a game since 2022. It was then a slightly naive attempt at a stoppage time counter attack, giving the ball away in a poor area, that directly led to Galeno’s stunning last-gasp winner for Porto. “Obviously we’re very disa…