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.
Agreed, there is no point of sitting and whining about decisions that are already. I also think it is time to move on from the past and look forward to the future of the club, its time to focus on improvement and Bayern at the moment needs a new striker which should be looked into probably in the January transfer window or looking out for free agents to strengthen Bayern's attack.