move all of the folders (except data and config) to an other place to be safe (u could delete also because of backup.)
extract the new version (proof the owner)
and open up the webpage or use occ update Option
i think a link is malformed, so the redirect to the nextcloud-Server doesn’t perform right.
Maybe you should check the config.php. The problem would be kick the at the next update back if it 's still in.