UEFA champions league is for the best clubs. The struggles of Bayern Munich is as a result of the outstanding performance of Bayer Leverkusen this season. They're presently the main top rival for the title and Xabi Alonso doesn't appear to be relenting because there's more to accomplish with the current team. Bayern Munich will not give up on both sides because they're promising team and also formidable on the ground. Thomas Tuchel have targets this season and one of them is winning the Bundesliga title and also lifting the UEFA Champions League with this current outstanding team.
The best teams from various leagues across Europe are usually conveyed to participate in the champions league and that's why I do say thst no team in the champions league is a small team because they have all at some point been champions in their various leagues and that's why they qualified to participate in the champions league so for that alone they ain't small team except for that some of them don't have big names.
Teams like PSV who literal topped their league with over 12 points and still counting and still didn't find it challenging to get pass the group stage but couldn't make it pass the round of sixteen, they are a relatively big name because in their domestic league they are a champion and chances are they will still be in the champions league again by next season so they are a big team aswell and that's how I do rate some of these champions league teams except that some of them are more experienced than the other and uses that as an advantage over others.
Bayern Munich isn't a weak team and by all standard are supposed to make this game very tough for Arsenal even if they are playing from home and if para venture Arsenal wins then it could be said that they were the best team and deserved it but otherwise then the best team should proceed to the next stage of the league and hope too be the champions or probably finish at one amongst the first to third position.