Xabi Alonso has formed a strong mentality in his players, they can also play very well when facing a strong team like Bayern Munich. The challenge that Leverkusen will face is greater after it is confirmed that they will play in the Champions League next season, they will spend more time facing strong teams who will test their abilities.
Qualifying as a team that has never lost in the Bundesliga will not have much influence because the team level there is stronger and has experience on the European stage. They have learned many things in the Europa League, defeat in the final is a valuable lesson for Leverkusen, the slightest mistake can make them eliminated faster because the Champions League is more competitive than the Europa League.
Everyone knows how important Xabi's role was in turning Leverkusen's game into a very strong one. I think they are very ready for a competition as big as the Champions League. and they will be able to compete with other strong European teams.
they prepare better, I'm sure they won't end up like Napoli last season. where they won Serie A but then they had great difficulty competing with other teams both in Serie A and in the Champions League.