Shell instructions as follows:

sudo apt update && sudo apt upgrade --assume-yes && sudo apt full-upgrade --assume-yes && sudo apt autoremove -y

Updating the pi4/pi5 EEPROM

sudo rpi-eeprom-update

Updating the pi firmware

sudo rpi-update

Updating the OS Version from bullseye to bookworm

in etc/apt/sources.list & etc/apt/sources.list.d/raspi.list
Change the word bullseye to bookworm