Let's start with your network, because that's your most important issue. From what you've posted, I still believe your network is incorrectly provisioned, because the package for icu4c071.1v0 is available for the amd64 architecture 7.2-release in the Project's mirrors.
Issue the ping(1) command with a well known Internet site, such as $ ping -c 1 daemonforums.org. If your resolver is working properly, it should resolve the domain name to an IP address, reach out to the IP address and receive an echo, such as:
Code:
$ ping -c 1 daemonforums.org
PING daemonforums.org (65.109.3.37): 56 data bytes
64 bytes from 65.109.3.37: icmp_seq=0 ttl=236 time=138.874 ms
--- daemonforums.org ping statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 138.874/138.874/138.874/0.000 ms
If it doesn't resolve, you know your domain name resolution is not provisioned properly. If it resolves but fails to reach the server you'll know you have some sort of network connectivity issue. If resolution is not functioning properly, you should inspect the contents of /etc/resolv.conf for its nameserver entries, if any.
Next, reviewing your console output:
The easiest tool to review prior console output is with Shift-PgUp. Additionally, you can "log" your console session (including all keyboard entries, including backspaces and carriage returns) with the script(1) utility, and the terminal multiplexor tmux(1) can also pipe virtual terminal "pane" output to files. You can also use most shells to pipe standard output and/or standard error output to files. There are many ways to capture this information.
Lastly, exiting root's ksh(1) shell from su(1).
You have it right. When you are in a superuser shell your default prompt includes the pound-sign "#" to warn you of your administrative status. When you then use the "exit" command or CTRL-D to exit from that shell, your default prompt will then show the dollar-sign "$" to inform you that you are functioning as a normal user.