maurice@x-GA-78LMT-USB3-6-0:~$ sudo apt update
[sudo] password for notme:
Get:1 file:/var/opt/amdgpu-pro-local ./ InRelease
Ign:1 file:/var/opt/amdgpu-pro-local ./ InRelease
Get:2 file:/var/opt/amdgpu-pro-local ./ Release [814 B]
Get:2 file:/var/opt/amdgpu-pro-local ./ Release [814 B]
Get:3 file:/var/opt/amdgpu-pro-local ./ Release.gpg
Ign:3 file:/var/opt/amdgpu-pro-local ./ Release.gpg
Hit:4 http://de.archive.ubuntu.com/ubuntu xenial InRelease
Hit:5 http://de.archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit:6 http://de.archive.ubuntu.com/ubuntu xenial-backports InRelease
Hit:7 http://ppa.launchpad.net/dhor/myway/ubuntu xenial InRelease
Hit:8 http://archive.canonical.com/ubuntu xenial InRelease
Hit:10 http://repository.spotify.com stable InRelease
Hit:11 http://ppa.launchpad.net/inameiname/stable/ubuntu xenial InRelease
Get:9 http://deb.playonlinux.com trusty InRelease [2.590 B]
Hit:12 http://security.ubuntu.com/ubuntu xenial-security InRelease
Ign:13 http://archive.ubuntu.com/ubuntu trusty InRelease
Hit:14 http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu xenial InRelease
Hit:15 http://ppa.launchpad.net/webupd8team/tor-browser/ubuntu xenial InRelease
Hit:16 http://archive.ubuntu.com/ubuntu trusty Release
Ign:17 https://mega.nz/linux/MEGAsync/xUbuntu_16.04 ./ InRelease
Get:18 https://mega.nz/linux/MEGAsync/xUbuntu_16.04 ./ Release [988 B]
Get:19 https://mega.nz/linux/MEGAsync/xUbuntu_16.04 ./ Release.gpg [481 B]
Err:9 http://deb.playonlinux.com trusty InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 73F0D6E88E3D6C3A
Get:21 https://mega.nz/linux/MEGAsync/xUbuntu_16.04 ./ Packages [2.979 B]
Fetched 7.038 B in 1s (5.326 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
155 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://deb.playonlinux.com trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 73F0D6E88E3D6C3A
W: Failed to fetch http://deb.playonlinux.com/dists/trusty/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 73F0D6E88E3D6C3A
W: Some index files failed to download. They have been ignored, or old ones used instead.