I think your expectations about Barcelona and De Jong are already difficult to come true because it seems that the agreement with MU regarding the De Jong issue is only a matter of time for now especially when you look at the current price match and see from their condition that they need money especially in this case Fabrizio Romano have also spoken, it is very likely that an agreement will occur for the next few days.
I also still feel that this will be an interconnected chain when De Jong is agreed so Lewandowski is definitely going to Barcelona.
I might be exaggerating a bit to expect De Jong to be kept by Barcelona, but it is something that has to be decided well because De Jong has good prospects in midfield. Even if Barcelona have to sell him then I can't do much even though I would prefer him to stay for a few more seasons. Then from that, if Barcelona sold De Jong to Manchester United just to buy Lewandowski at the offered price, then I would definitely think that it would be an inappropriate move because Lewandowski will not have many seasons with Barcelona. He will probably only have a maximum of 3 seasons, that would be a disadvantage from a business point of view due to his high price tag. But there may be other things Barcelona are considering including De Jong's high salary and the value of a new contract extension.