Bayern still keep Lewandowski for two reasons, firstly his contract is still running until 2023 and secondly because his payment is still not in accordance with Bayern's proposal of 50 million euros. And Barcelona's offer for Lewandowski is still below that price which makes Bayern continue to keep him.
The situation will be very complicated and depends on the offer that Barcelona gives but Barcelona will not give up on getting him, even though Lewandowski wants to go to Barcelona, it all depends on Bayern.
Yes you are right, Bayern Munich are in control of Lewandowski's transfer because they are still under contract. What happens to Barcelona if they fail to get Lewandowski, as time goes on. If they lingered with this one player, then they would be wasting time doing something else important. Barcelona must have an attitude now, because not once, but three times their proposal was rejected.