Ubuntu 16.04 apt update does not have a Release file

I can't install anything to ubuntu server and can't update it. My sources.list and other commands output is below. How can i fix it ?

$ sudo nano /etc/apt/sources.list

deb http://gb.archive.ubuntu.com/ubuntu/ xenial main restricted
deb http://gb.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
deb http://gb.archive.ubuntu.com/ubuntu/ xenial universe
deb http://gb.archive.ubuntu.com/ubuntu/ xenial-updates universe
deb http://gb.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://gb.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
deb http://gb.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://security.ubuntu.com/ubuntu xenial-security universe
deb http://security.ubuntu.com/ubuntu xenial-security multiverse

$ sudo apt update

Ign:1 http://gb.archive.ubuntu.com/ubuntu xenial InRelease
Ign:2 http://security.ubuntu.com/ubuntu xenial-security InRelease
Ign:3 http://gb.archive.ubuntu.com/ubuntu xenial-updates InRelease
Err:4 http://security.ubuntu.com/ubuntu xenial-security Release
  Connection failed [IP: 91.189.88.161 80]
Ign:5 http://gb.archive.ubuntu.com/ubuntu xenial-backports InRelease
Err:6 http://gb.archive.ubuntu.com/ubuntu xenial Release
  Connection failed [IP: 91.189.88.162 80]
Err:7 http://gb.archive.ubuntu.com/ubuntu xenial-updates Release
  Connection failed [IP: 91.189.88.152 80]
Err:8 http://gb.archive.ubuntu.com/ubuntu xenial-backports Release
  Connection failed [IP: 91.189.88.162 80]
Reading package lists... Done
E: The repository 'http://security.ubuntu.com/ubuntu xenial-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.
E: The repository 'http://gb.archive.ubuntu.com/ubuntu xenial 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://gb.archive.ubuntu.com/ubuntu xenial-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://gb.archive.ubuntu.com/ubuntu xenial-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.

$ wget http://security.ubuntu.com/ubuntu/dists/xenial-security/Release

--2018-11-27 19:00:09-- http://security.ubuntu.com/ubuntu/dists/xenial-security/Release
Resolving security.ubuntu.com (security.ubuntu.com)... 91.189.88.162, 91.189.88.152, 91.189.88.161, ...
Connecting to security.ubuntu.com (security.ubuntu.com)|91.189.88.162|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 105813 (103K)
Saving to: ‘Release.2’

Release.2 100%[=====================================================================================>] 103,33K 336KB/s in 0,3s

2018-11-27 19:00:11 (336 KB/s) - ‘Release.2’ saved [105813/105813]

$ wget 91.189.88.162

--2018-11-27 19:01:21-- http://91.189.88.162/
Connecting to 91.189.88.162:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 11321 (11K) [text/html]
Saving to: ‘index.html.1’

index.html.1 100%[=====================================================================================>] 11,06K --.-KB/s in 0,02s

2018-11-27 19:01:22 (528 KB/s) - ‘index.html.1’ saved [11321/11321]

$ lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial