I'm used to splitting windows usind F3 in ubuntu, but in ubuntu GNOME it does't work. How do I fix that?
That functionality (and a few others) were removed when Nautilus 3.6 was introduced to GNOME. It is one of the good reasons why Unity is diverging from GNOME and why the Mint folks came up with Cinnamon. Unity uses Nautilus 3.4, the last fully functional release.
Luckily for you it is possible to downgrade from Nautilus 3.6 to 3.4.