If it were Napoli's decision alone to make about the future of Victor Osimhen, the news about his transfer would have been a thing of the past because Napoli are so keen to have him go to Saudi due to the fees the Saudi club are willing to offer in full. But the striker just as you said wants to play in Europe so desperately and am glad that Galatasaray are making all efforts to retain him in their club. A lot of respect there for Gala... It shows a lot of value they have for the Nigerian striker's role he played in their clubs successes last season.
It is definitely a good club and I am sure Osimhen is happy to be playing at this club, but I also think that he would like to leave Galatsaray in the future and play for another European team that has more potential, for example in the Champions League. Or play in a more prestigious league, EPL for example, where the competition is very high. This would raise his level as a player
Surely he is happy and in turn the club is also happy with him which has led to their push towards retaining Osimhen in the club. Some of the EPL clubs that have been coming for him are unwilling to pay for the fees Napoli placed on him and with his wage he is demanding for . But I don't see it as something too much to ask for, provided the player is giving the required results, of which Osimhen has proven many times every club he plays for.