Galatasaray are looking pretty serious this season, they made quite a number of additions to their squad this summer, if I am not mistaken they signed up to 13 players in this transfer window including Victor Osimhen, Iker Gundogan, Sane and a couple more so What do you expcect. If after this signing there is still no significant improvement then it will be a problem.
Galatasaray has built a strong squad, but I doubt they can succeed in the Champions League. Turkish teams always struggle in European competition. It's certainly good that the squad has improved, but Osimhen and other players aren't enough to propel this team to the top.
They certainly have a chance in other competitions, but they're definitely not a strong enough team for the Champions League
It doesn't just depend on the players. You can only have star players but it won't be enough for the CL if the coach isn't good. The coach is responsible for ensuring that the tactics are good and only good tactics in combination with strong players can ensure that you progress in the Champions League and have a chance of winning the CL!