The shell commands you used are not supported on the Greenbone Security Manager. They are blocked on purpose and the output you posted is the expected behaviour. Please only use the Greenbone OS Administration menu to update the feed.
If updating the feed does not work, the problem needs to be analyzed:
First, make sure that your GSM TRIAL is directly connected to the internet and that it can resolve the domain name
feed.community.greenbone.net. Using a shared proxy or shared VPN can cause problems, see the second point below.
Second, to prevent abuse of our free service, we limit the number of connections to the Greenbone Community Feed server. If you make more than 10 connections from the same IP address within 1 minute, or if you try to connect multiple times in parallel, the IP address will be blocked for 24 hours. If this is the case, try again after 24 hours.
Last but not least, running a feed update will take some time to finish. After you have started it from the menu, check regularly in the “About” menu to see if it is still in progress, and do not power off your GSM TRIAL during this time.