Dries Mertens will play as a left winger, Hakim Ziyech plays as a right winger. I think Galatasaray coach will use this duo players for the wingers. But it will be quite confusing if one of this players got injured. There is no more option for a left winger if Mertens injured. Well, I can understand that Galatasaray has too many right wingers, they have no pure left winger.
However, it is good that Galatasaray signs Osimhen. It is a food addition player for Galatasaray. With 4 strikers in the squad, I think Galatasaray coach may use an option to play with 2 strikers.
Mertens should
never play as a LW. Because he can't run, he has got really old (37). He should be used as a second striker or midfielder. If Okan Buruk changes the formation to 3-5-2, we would see him in the middle. If we see a formation like 3-4-1-2 then he can play as a CAM. I would rather seeing the latter as it is closer to his natural position.

I think they can do like this: Barış Alper on the left and Ziyech on the right. Because Barış Alper is right-footed while Ziyech is left-footed. In this way they can easily shoot when there is opportunity too.
It is quite unfortunate that Kerem Aktürkoğlu moves to Benfica. He is the only left winger of Galatasaray. I don't understand why he prefers to leave, is about the amount of salary? He has no problem with his position, he is in the main lineup. He has a regular place as a left winger, and he always becomes a part of starting lineup in every match. Does he has a problem with Galatasaray board, coach, or the players?
I agree. There was just no plan by Galatasaray board. They left all the necessary transfers to the last moment and this happened.

A LW and and a midfielder was urgent. Now even if they sign players for these positions, they won't be able to register in the Europa League until league phase ends.