After some attempts trying to install Nvidia driver on Debian, I found a solution.
After following the steps explained on Debian wiki I restarted my computer and then a screen popped up…
I logged in tty console (Ctrl+Alt+F1), opened up Xorg log but there weren’t any errors (of course it’s Gnome’s problem(facepalm)), anyway… After some digging, I found out that the problem was the not “refreshed” update-alternatives.
update-alternatives --config glx
and set it to mesa-diverted
So thanks to this bug post I have a fully working bumblebee-nvidia installation