I have not yet seen any rumors that Cristiano Ronaldo is interested in going to Bayern Munich. He joined Manchester United last season. It doesn't seem credible to me that he will leave United this season. However, if Ronaldo comes to Bayern Munich, I don't think he will be able to get along well with Lewandowski. Lewandowski has long been one of Bayern Munich's most important players. He certainly does not want to lose his position.
I have read that the agent of Cristiano Ronaldo has offered him to Bayern Munich, but that is not really something special during the summer transfer period. Agents are contacting a lot of clubs to find new clubs for their players or only to improve the negotiation situation for their clients with it's current club. Even if Cristiano Ronaldo would like to go to Bayern Munich i hardly doubt that Bayern Munich itself has any interest in signing Ronaldo. He is already 37 years old and it is said that he is earning 30 Million € after taxes currently at Manchester United. That is way more than the current top earner at Bayern gets (24 Million € before taxes).