The reason for the improvement in Leverkusen's performance could be attributed to the number of games they have played and the challenges they have faced althrough this season and how much errors they made during those matches most especially how much they have managed to improve on all of these errors, I think all these and many more have helped shaped the team and probably made them appear to be a better side than Bayern Munich perhaps they might overtake Bayern Munich to the top by January or Munich might fix their loopholes and resist from giving up their position by improving more on their performance.
Yea, it is always good to learn from your mistake and take advantage of it to make positive changes. Alonso is a wise coach, he tried his best to study the team and their weakness, he then improvise to get a temporary solution which he got, they are now playing really well as they has gone like seven matches winning streak which is very good for the team, and this will make the Bundesliga more competitive because in the beginning of the season, it seems like Bayern Munich has taken over the dominance in the Bundesliga, but Alonso is back to make Leverkusen fans proud and happy again.
I was happy to see that Leverkusen is stable currently, and they have put themselves back as the rival to Bayern in the title race. Alonso is a good and skillful coach that knows how to overcome whatever challenges that arises in the team performance.
However, Bayern has been doing pretty good since Kompany took over the club. The title race will be fierce because Leverkusen will not give up on defending the title this season.