Bayern Munich seems reluctant to let Joshua Kimmich go but unfortunately, it is not in line with what the player concerned wants because as far as I know, Joshua Kimmich is not interested in extending his contract, which means he could leave this January or at the end of the season as a free agent. Besides Real Madrid, Liverpool is also reportedly interested in Joshua Kimmich. It seems like Liverpool wants to anticipate if Trent Alexander Arnold really leaves Anfield.
Since Kimmich is one of the main players in Bayern Munich, they should reject any offer for Kimmich. However, I agree that Bayern Munich is possible to let him moving to Real Madrid if Kimmich has no longer interested to stay. There is no point in keeping a player who has no longer interest to stay. It probably just ruins the compactness and performance of the whole team. And he may decline his performance if he is forced to stay. So, it is better to sell him and get good amount of money for buying a new player.
There must be many clubs which are interested to sign Kimmich. But Kimmich probably prefers Real Madrid if he wants to dream of UCL title. However, he can move to Liverpool if he wants to play in the biggest domestic league in the world. EPL is still number 1 European league, and it is number 1 in the world.