sudo apt update - proxy

how to use proxy in ubuntu?

here are few commands that might help
env | grep proxy
unset no_proxy
sudo nano /etc/environment
  PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"
  http_proxy="http://proxy.company.com:port/"
  https_proxy="https://proxy.company.com:port/"
  ftp_proxy="ftp://proxy.company.com:port/"

env | grep proxy
sudo apt update
sudo apt upgrade

sudo nano /etc/apt/sources.list (make sure use the default settings from another computer)