Hello,

Firstly you can use Osmanbey- Hacıosman metro to İTÜ Ayazağa metro station. When you reach İTÜ Ayazağa metro station you can use mini-bus to Tarabya  or you can use 40B Beşiktaş - Sarıyer number bus. But mini-bus is better choice because you dont wait.

Hope information helps you