I'm new to Ubuntu. Got this error while installing ppa:

You seem to have a lot of repositories that are non-functional or missing items for 16.04. You will need to remove or update these items to get rid of these errors.
Go to Settings (the gear icon) and choose Software & Updates. Click on the Other Software tab and remove the entries that are giving you the errors. It will ask for a password. Just enter your login password and once those entries are removed you will no longer get errors.