title: Sudo apt-get update problem, it is always showing me "404 error" & "release is not available"
body: <p>I know there are many answers to this but i already tried many solutions on internet but not a single one worked for me .
  Im using Ubuntu 19.04 in an Oracle virtual Box.</p>
  <pre><code>ather@ather-VirtualBox:~$ sudo apt-get update
  [sudo] password for ather: 
  Ign:1 http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04  InRelease
  Ign:2 http://security.ubuntu.com/ubuntu disco-security InRelease
  Err:3 http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04  Release
    404  Not Found [IP: 195.135.221.134 80]
  Ign:4 http://in.archive.ubuntu.com/ubuntu disco InRelease
  Ign:5 http://in.archive.ubuntu.com/ubuntu disco-updates InRelease
  Err:6 http://in.archive.ubuntu.com/ubuntu disco Release
    404  Not Found [IP: 43.255.166.254 80]
  Err:7 http://in.archive.ubuntu.com/ubuntu disco-updates Release
    404  Not Found [IP: 43.255.166.254 80]
  Err:8 http://security.ubuntu.com/ubuntu disco-security Release
    404  Not Found [IP: 91.189.91.39 80]
  Reading package lists... Done
  E: The repository 'http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04  Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  E: The repository 'http://in.archive.ubuntu.com/ubuntu disco Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  E: The repository 'http://in.archive.ubuntu.com/ubuntu disco-updates Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  E: The repository 'http://security.ubuntu.com/ubuntu disco-security Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  </code></pre>
  <p><a href="https://i.stack.imgur.com/L5BTm.png" rel="nofollow noreferrer">Software Configuration is like this</a></p>