Upgrade it
  sed -i 's/stretch/buster/g' /etc/apt/sources.list
  sed -i 's/buster/bullseye/g' /etc/apt/sources.list
**Debian 11**
  deb http://deb.debian.org/debian/ bullseye main contrib non-free 
  deb http://deb.debian.org/debian/ bullseye-updates main contrib non-free
  deb http://deb.debian.org/debian bullseye-proposed-updates main contrib non-free
  deb http://deb.debian.org/debian-security/ bullseye-security main contrib non-free
  deb http://deb.debian.org/debian/ bullseye-backports main contrib non-free
**Debian 10**
  deb http://deb.debian.org/debian buster main
  deb-src http://deb.debian.org/debian buster main
  deb http://deb.debian.org/debian-security/ buster/updates main
  deb-src http://deb.debian.org/debian-security/ buster/updates main
  deb http://deb.debian.org/debian buster-updates main
  deb-src http://deb.debian.org/debian buster-updates main
**Debian 9**
  deb http://deb.debian.org/debian stretch main
  deb-src http://deb.debian.org/debian stretch main
  deb http://deb.debian.org/debian-security/ stretch/updates main
  deb-src http://deb.debian.org/debian-security/ stretch/updates main
  deb http://deb.debian.org/debian stretch-updates main
  deb-src http://deb.debian.org/debian stretch-updates main