add sources list

enter command sudo nano /etc/apt/sources.list then paste these lines down there :

# deb cdrom:[Debian GNU/Linux 12.7.0 _Bookworm_ - Official amd64 DVD Binary-1 with firmware 20240831-10:40]/ bookworm contrib main non-free-firmware

deb https://deb.debian.org/debian bookworm main non-free-firmware
deb-src https://deb.debian.org/debian bookworm main non-free-firmware

deb https://security.debian.org/debian-security bookworm-security main non-free-firmware
deb-src https://security.debian.org/debian-security bookworm-security main non-free-firmware

deb https://deb.debian.org/debian bookworm-updates main non-free-firmware
deb-src https://deb.debian.org/debian bookworm-updates main non-free-firmware