Yes, it seems to be very difficult to bring Lewandowski to this club. However, Bayern Munich also doesn't seem to want to let Lewandowski go. Now it's just a matter of how the negotiations will proceed and Barcelona's financial strength to make this happen.
Of course, as long as Lewandoski has a contract with Munchen he should be able to respect that. Although in some media it was stated that he wanted to leave because of his own will. Munchen have calmed down because they got Mane, although Lewandoski's form later dropped because he was not happy. But if Munchen wait until his contract runs out they will lose, because he will leave on a free transfer. I think they kept Lewandoski in for barcelona to bid even higher.