No matter what happens, in the end, the main conclusion that can be drawn from this match is that Bayern Munich is struggling to score goals, and that is going to be a major concern in their upcoming matches. My opinion is that one of their biggest mistakes was selling Robert Lewandowski to FC Barcelona. As I believe that Robert Lewandowski was the main goal scorer for Bayern at the time, scoring almost 400 goals for them. Which is really quite an impressive number, and he was a powerful goal scorer in front of the target, which is something Bayern does not have right now.
Selling Lewandowski is a thing of the past - there is no point in talking about how good it would be if he stayed or something like that. Now Nagelsmann has to work with what he has - either change the game plan, taking into account the fact that Bavaria does not have a center forward, or endure until the winter transfer window and buy Ronaldo (this will be the only option in winter). I don't see any other options given the state of the market and the frugality of Bavaria.
Losing Lewandowski is indeed a big loss for Bayern Munich but I don't think this can be considered a mistake because Lewandowski really wanted to leave Bayern Munich and if Bayern did everything they could to keep Lewandowski at Munich, I think it can affect Lewandowski's performance and motivation in playing football (it could be that Bayern Munich's performance is much worse than it is now). So when an agreement has been reached, all Bayern Munich needs to do is find a player to replace Lewandowski.