Software Center (Check your Internet connection)

Can you give the output of:

sudo apt-get update; sudo apt-get upgrade

Do you use a proxy for web access?

This is the out put you asked for

Err http://archive.canonical.com oneiric InRelease

Err http://us.archive.ubuntu.com oneiric InRelease

Err http://us.archive.ubuntu.com oneiric-updates InRelease

Err http://security.ubuntu.com oneiric-security InRelease

Err http://archive.canonical.com oneiric Release.gpg
  Unable to connect to 213.158.112.202:8080:
Err http://security.ubuntu.com oneiric-security Release.gpg
  Unable to connect to 213.158.112.202:8080:
Err http://us.archive.ubuntu.com oneiric Release.gpg
  Unable to connect to 213.158.112.202:8080:
Err http://us.archive.ubuntu.com oneiric-updates Release.gpg
  Unable to connect to 213.158.112.202:8080:
Reading package lists... Done
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/oneiric/InRelease

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/oneiric-updates/InRelease

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/InRelease

W: Failed to fetch http://archive.canonical.com/ubuntu/dists/oneiric/InRelease

W: Failed to fetch http://archive.canonical.com/ubuntu/dists/oneiric/Release.gpg Unable to connect to 213.158.112.202:8080:

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/oneiric/Release.gpg Unable to connect to 213.158.112.202:8080:

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/oneiric-updates/Release.gpg Unable to connect to 213.158.112.202:8080:

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/Release.gpg Unable to connect to 213.158.112.202:8080:

W: Some index files failed to download. They have been ignored, or old ones used instead.
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
  file-roller
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 464 kB of archives.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]? y
Err http://us.archive.ubuntu.com/ubuntu/ oneiric-updates/main file-roller i386 3.2.1-0ubuntu2
  Could not connect to 213.158.112.202:8080 (213.158.112.202). - connect (111: Connection refused)
Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/f/file-roller/file-roller_3.2.1-0ubuntu2_i386.deb Could not connect to 213.158.112.202:8080 (213.158.112.202). - connect (111: Connection refused)
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

and about the proxy .. i recently tried to install a proxy server app but honestly i don't know what happened it didn't work .. and i couldn't find it to uninstall it .. i'm new to Ubuntu i don't have much experience in using it, if there's anyway to reset my proxy or something like that i think it will do it

I forgot to thank you :) I really appreciate what your doing ^_^

i have another thing its not related to this question but i hope u can help me solving it .. i can't adjust my screen brightness using the keyboard shortcut also the manual way through settings doesn't affect anything

http://proxy-checker.net/proxy/213.158.112.202-8080

Yes, you are using a proxy, you will need this to make apt use the proxy (or just use a direct connection by undoing the changes you made).

http://www.linuxquestions.org/questions/fedora-35/how-to-set-up-proxy-in-apt-gets-apt-conf-265793/

You may want to use a different proxy if that one is ceased. Can you ping the proxy IP...?

        Thank you so much andrew-woodhead666,

My problem is now solved i have been undoing all proxy setting which i have made earlier and it worked out just fine :D