These are the only two command that lets you install the latest Mozilla Firefox Quantum on your Linux Debian
first download the latest Firefox version available
wget -O FirefoxSetup.tar.bz2 "https://download.mozilla.org/?product=firefox-latest&os=linux64&lang=en-US"
than create the directory
mkdir /opt/firefox
untar the latest Firefox version in the new directory
tar xjf FirefoxSetup.tar.bz2 -C /opt/firefox/
Optional:
Make a backup of the original Firefox binary shipped with Debian and create a new symbolic link pointing to downloaded Firefox executable:
mv /usr/lib/firefox-esr/firefox-esr /usr/lib/firefox-esr/firefox-esr_orig
ln -s /opt/firefox/firefox/firefox /usr/lib/firefox-esr/firefox-esr
Restore Debian’s Default
unlink /usr/lib/firefox-esr/firefox-esr
mv /usr/lib/firefox-esr/firefox-esr_orig /usr/lib/firefox-esr/firefox-esr
Thanks to Lubos Rendek