The true story is that he rejected Hilal's proposal, and wanna stay in Galatasaray much longer. The problem is that he wants increased salary from Galatasaray, which is impossible to happen. though he's Galatasaray's top scorer. Things getting even complicated when his contract becomes even shorter. That's the reason Napoli wanna recoup some money by selling him.
Even if he already rejected Hilal's proposal, but Napoli has not said no to the Hilal's proposal.
Osimhen didn't outrightly reject the move to Al Hilal, he turned down the salary because it was small. Currently, there's a second, improved offer on the table. Also, Galatasaray is fighting to keep him, but he hasn't accepted any deal. Any news about him signing with Al Hilal or Gala is just rumors, nothing has been finalized yet. If I were to guess where he'll be playing next season, I'd say the SPL. Gala cannot match up his salary.