apt-get не работает, и я не могу ничего установить (проблема с обновлением) [закрыто]

Я запускаю ubuntu 16.04 и обнаружил, что больше не могу устанавливать пакеты. Что бы я ни пытался, я получаю такие сообщения, как

Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created or
been moved out of Incoming. 

The following information may help to resolve the situation:
The following packages have unmet dependencies:  
   anydesk : Depends: libgtkglext1 but it is not installable 
E: Unable to correct problems, you have held broken packages.

Я где-то читал, что мне следует запустить apt update , но это не работает. Он отображает следующее:

Ign:1 http://security.ubuntu.com/ubuntu artful-security InRelease
Ign:2 http://archive.ubuntu.com/ubuntu artful InRelease 
Err:3 http://security.ubuntu.com/ubuntu artful-security Release   404  Not Found [IP: 91.189.88.161 80] 
Ign:4 http://archive.ubuntu.com/ubuntu artful-updates InRelease 
Ign:5 http://archive.ubuntu.com/ubuntu artful-backports InRelease 
Err:6 http://archive.ubuntu.com/ubuntu artful Release   404  Not Found [IP: 91.189.88.161 80] 
Err:7 https://archive.ubuntu.com/ubuntu artful-updates Release  404  Not Found [IP: 91.189.88.161 80] 
Err:8 http://archive.ubuntu.com/ubuntu artful-backports Release   404  Not Found [IP: 91.189.88.161 80]
Reading package lists... Done 
E: The repository 'http://security.ubuntu.com/ubuntu artful-security Release' no longer has 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 'archive.ubuntu.com/ubuntu artful 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 'archive.ubuntu.com/ubuntu artful-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 'archive.ubuntu.com/ubuntu artful-backports 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.

Я уже пробовал sudo apt-get -f install , но у меня не установлено synaptic (и я не могу его установить по очевидным причинам).

Что мне делать?