ubuntu update error

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