Apt encounters errors with bad GPG keys [duplicate]

Solution 1:

Your BADSIG Problem is an easy one. Your signatures are incorrect. Update them with:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 40976EAF437D05B5

Please do that with every wrong key by just changing the last key number and keeping the rest.

Rebuild your software cache:

cd /var/lib/apt
sudo mv lists lists.old
sudo mkdir -p lists/partial
sudo apt-get update

Maybe that will fix your Software Center Problem as well.

PS: But if you ask here - many nice people will surely help you here and you will learn a lot! But please keep on giving as much error output as possible.