Can't install anything from ubuntu Software Center 16.04.3

Question

I've seen this problem in a lot of forums, but it looks like is not exactly the same. I'll explain:

I'm trying to install the 'Pinta' Software from Ubuntu's Software Center. I get this error message:

A continuación se muestran los errores detallados del gestor de paquetes:

apt transaction returned result exit-failed

I searched, and people says I must change the Ubuntu's Software Center Server. I'm from Argentina, so I had that server selected. When I change it to the main server, and reload, i get this error message:

W:The repository 'http://ppa.launchpad.net/yannubuntu/boot-repair/ubuntu xenial Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details.,
W:The repository 'http://archive.ubuntu.com/ubuntu xenial Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:The repository 'http://archive.ubuntu.com/ubuntu xenial-updates Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:The repository 'http://archive.ubuntu.com/ubuntu xenial-backports Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:The repository 'http://archive.ubuntu.com/ubuntu xenial-security Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:The repository 'http://dl.google.com/linux/chrome/deb stable Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:The repository 'http://repository.spotify.com stable Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., 
W:Failed to fetch https://download.sublimetext.com/apt/stable/InRelease  Failed to connect to download.sublimetext.com port 443: No route to host, 
E:Failed to fetch http://ppa.launchpad.net/yannubuntu/boot-repair/ubuntu/dists/xenial/main/source/Sources  Unable to connect to ppa.launchpad.net:http:, 
E:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/restricted/binary-amd64/Packages  Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1560:8001::11). - connect (101: Network is unreachable) [IP: 2001:67c:1560:8001::11 80], 
E:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/main/binary-amd64/Packages  Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1560:8001::11). - connect (101: Network is unreachable) [IP: 2001:67c:1560:8001::11 80], 
E:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-amd64/Packages  Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1560:8001::11). - connect (101: Network is unreachable) [IP: 2001:67c:1560:8001::11 80], 
E:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-security/main/binary-amd64/Packages  Cannot initiate the connection to archive.ubuntu.com:80 (2001:67c:1560:8001::11). - connect (101: Network is unreachable) [IP: 2001:67c:1560:8001::11 80], 
E:Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/main/binary-amd64/Packages  Cannot initiate the connection to dl.google.com:80 (2800:3f0:4002:806::200e). - connect (101: Network is unreachable) [IP: 2800:3f0:4002:806::200e 80], 
E:Failed to fetch http://repository.spotify.com/dists/stable/non-free/binary-amd64/Packages  Unable to connect to repository.spotify.com:http: [IP: 54.230.84.32 80], 
W:Some index files failed to download. They have been ignored, or old ones used instead.

In other posts it says that the problem happen when we try to download an incorrect version of our softwares, but as you can see, i'm downloading always the xenial versions.

I'm under a proxy here, but all my configurations are ok, because my partners have the same configuration, and they don't have this problem.

My /etc/apt/sources.list file is this:

# deb cdrom:[Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (20170801)]/ xenial main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://archive.ubuntu.com/ubuntu xenial main restricted
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://archive.ubuntu.com/ubuntu xenial-updates main restricted
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://archive.ubuntu.com/ubuntu xenial universe
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial universe
deb http://archive.ubuntu.com/ubuntu xenial-updates universe
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://archive.ubuntu.com/ubuntu xenial multiverse
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://archive.ubuntu.com/ubuntu xenial-updates multiverse
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://archive.ubuntu.com/ubuntu xenial-backports main restricted universe multiverse
# deb-src http://ar.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu xenial partner
# deb-src http://archive.canonical.com/ubuntu xenial partner

deb http://archive.ubuntu.com/ubuntu xenial-security main restricted
# deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://archive.ubuntu.com/ubuntu xenial-security universe
# deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://archive.ubuntu.com/ubuntu xenial-security multiverse
# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
# deb [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable
# deb-src [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable

My partners have the same file.