To remove the confirmation every time you shutdown or reboot, type this into the terminal.
gsettings set org.gnome.SessionManager logout-prompt falseTo remove the GRUB (the GRand Unified Bootloader) option during startup to boot faster, add
GRUB_RECORDFAIL_TIMEOUT=0to the file /etc/default/grub. (sudo is required to edit). eg:
sudo nano /etc/default/grubGRUB is basically a boot loader that helps uses to choose what OS they want to boot into.