Verify that you have minimal repositories by using
cat /etc/apt/sources.list
You should have these entries :
deb http://deb.debian.org/debian buster main contrib non-free deb http://deb.debian.org/debian buster-updates main contrib non-free deb http://deb.debian.org/debian/ buster-proposed-updates main contrib non-free deb http://deb.debian.org/debian/ buster-backports main contrib non-free deb http://security.debian.org/ buster/updates main contrib non-free
Modify them according to using this command line
echo "deb http://deb.debian.org/debian buster main contrib non-free" > /etc/apt/sources.list && echo "deb http://deb.debian.org/debian buster-updates main contrib non-free" >> /etc/apt/sources.list && echo "deb http://deb.debian.org/debian/ buster-proposed-updates main contrib non-free" >> /etc/apt/sources.list && echo "deb http://deb.debian.org/debian/ buster-backports main contrib non-free" >> /etc/apt/sources.list && echo "deb http://security.debian.org/ buster/updates main contrib non-free" >> /etc/apt/sources.list