Vojtěch,
Upgrade to Debian 9.
We will make a back up of your
sources.list file then change it to debian 9.
As root:
apt-get update && apt-get
upgrade
Then as root make a backup of sources
list.
cp /etc/apt/sources.list
/etc/apt/sources.list.bak
Change sources list from Debian 8 to
Debian 9.
sed -i 's/jessie/stretch/g' /etc/apt/sources.list
Now the sources.list has been updated.
Continue as root:
apt-get update && apt-get
upgrade && apt-get dist-upgrade
That will make you Debian 9.
You will have the correct files then.
Best regards,
David