Ошибка в хранилище с Ubuntu 16.04 (Xenial)

У меня проблема с запуском sudo apt-get update:

W:The repository 'http://old-releases.ubuntu.com/ubuntu xenial-security Release' does not have a Release file., 
W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., 
W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:The repository 'http://ppa.launchpad.net/ubuntu-audio-dev/ppa/ubuntu xenial Release' does not have a Release file., 
W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., 
W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:Failed to fetch http://de.old-releases.ubuntu.com/ubuntu/dists/xenial/InRelease  Could not resolve 'de.old-releases.ubuntu.com', 
W:Failed to fetch http://de.old-releases.ubuntu.com/ubuntu/dists/xenial-updates/InRelease  Could not resolve 'de.old-releases.ubuntu.com', 
W:Failed to fetch http://de.old-releases.ubuntu.com/ubuntu/dists/xenial-backports/InRelease  Could not resolve 'de.old-releases.ubuntu.com', 
E:Failed to fetch http://old-releases.ubuntu.com/ubuntu/dists/xenial-security/main/binary-amd64/Packages  404  Not Found, 
E:Failed to fetch http://ppa.launchpad.net/ubuntu-audio-dev/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found, 
W:Some index files failed to download. They have been ignored, or old ones used instead.

я должен добавить какой-либо другой репозиторий?