Bayern Munich made a big mistake by allowing Robert Lewandowski to leave the club. He was one of the most prolific goal scorers that they have ever had. There is no doubt that he is someone who can score at any time of the match, no matter what the circumstances are. However, he was sold to Barcelona and Sadio Mane was brought in to play the center-forward position which is not his natural position, which was not the right choice for him. Yes, we understand that they have the ability to get any player that they want. The thing is that they should have brought in an actual striker first and then sold Robert Lewandowski. But right now they are in jeopardy of losing the Bundesliga title.
You don't force players to remain in a club. Robert Lewandowski really wanted to leave the club and it would be counter-productive to force him to stay. An example of the effect of forcing players to remain in the club is Cristiano Ronaldo. He wanted to leave for a Champions League club but Manchester United was unwilling to let him leave. This can lead to some psychological problems that would definitely affect the performance of the player. Since then, Ronaldo has been a shadow of himself, scoring fewer goals.
The summer transfer window was very competitive, making it difficult to attract quality players. Barcelona was the most favored club in this transfer window. The truth is that Bayern Munich have not gotten the right replacement for Lewandowski and I am sure if they are patient the club would be able to attract one. The January window would be a very good opportunity for the club to get a suitable central striker. And I am even suggesting that they should get a younger sticker that would play for the team for a long time.