Hallo wolfman,
unfortunately I am ill, so today an tomorrow there will be no activities. But the hint via “WELCOME” I did try with following result:
W:Target Packages (universe/binary-armhf/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Packages (universe/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Translations (universe/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Translations (universe/i18n/Translation-de) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Packages (main/binary-armhf/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Translations (main/i18n/Translation-de) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Packages (restricted/binary-armhf/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Packages (restricted/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Translations (restricted/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, W:Target Translations (restricted/i18n/Translation-de) is configured multiple times in /etc/apt/sources.list:1 and /etc/apt/sources.list:15, E:Failed to fetch http://de.archive.ubuntu.com/ubuntu/dists/xenial/main/binary-armhf/Packages 404 Not Found [IP: 141.76.1.204 80], E:Failed to fetch http://de.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-armhf/Packages 404 Not Found [IP: 141.76.1.204 80], E:Some index files failed to download. They have been ignored, or old ones used instead.
This is, what happens every time when I try to update the sources list via any GUI tool; not with apt-get update?
Will be back here on tuesday I hope
hfb