It's true that Killyan Mbappe is coming to real Madrid, but what's that "Vinices Jr. is leaving?" I don't know why why real Madrid is going to take a step like that. There won't be any problem if Vinice Jr. plays as a winger or Killyan Mbappe plays in the ST position. So I think it would be good because both are good players and if a team has a fast attacker like Vinice Jr or Mbappe, no defense can stop him. 
 
So it's meant to say that if Real madrid sells Vini to sign Killyan Mbappe then I think it's Real madrid's loss, they will lose a world class winger. But anyway I think it is just a rumor. I don't think real Madrid will sell Vinices jr.