Install Updates Error log Linux lite 4, please help

[rama1977]

Hello

I just started using linux lite4 and I am new to linux...
I tried to update but it failed and asked me to paste the log below for help. Please help if you can..?

============ Log ===========

Hit:1 http://archive.canonical.com/ubuntu bionic InRelease
Hit:2 http://ppa.launchpad.net/otto-kesselgulasch/gimp/ubuntu bionic InRelease
Hit:4 http://ppa.launchpad.net/teejee2008/ppa/ubuntu bionic InRelease
Hit:5 https://repo.skype.com/deb stable InRelease
Hit:6 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Get:3 http://ppa.launchpad.net/sebastian-stenz...tor/ubuntu bionic InRelease [15.9 kB]
Get:7 http://us.archive.ubuntu.com/ubuntu bionic-security InRelease [83.2 kB]
Get:8 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Err:3 http://ppa.launchpad.net/sebastian-stenz...tor/ubuntu bionic InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 892C15CD130FEB9A
Get:9 http://us.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Hit:10 http://repo.linuxliteos.com/linuxlite diamond InRelease
Get:11 http://us.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [290 kB]
Get:12 http://us.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [262 kB]
Get:13 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [161 kB]
Get:14 http://us.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages [161 kB]
Reading package lists...
W: GPG error: http://ppa.launchpad.net/sebastian-stenz...tor/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 892C15CD130FEB9A
E: The repository 'http://ppa.launchpad.net/sebastian-stenzel/cryptomator/ubuntu bionic InRelease' is not signed.

Regards
Rama

[Valtam]

https://github.com/cryptomator/cryptomator/issues/671

Remove the PPA and installl the Appimage as is mentioned in the above link.