Tushar, I think you are working under a misunderstanding.
This is a fan based News and Discussion site. It is in no way run by Microsoft, Lumia or any developers... So when you say "fix it," to this site; it's like pulling into a gas station and asking the people at the other gas pumps to change your fan belt. You are not going to get any attention, but maybe you'll draw some weird stares. Meanwhile, you still need your fan belt changed.
Now for your problem.
Microsoft has been having some legitimate server issues this week. It may be just that and nothing more
Your Microsoft Account may not be able to sync and this could cause the error also
Test to see if you can sync your Microsoft Account now. Settings > email + accounts > hold down on the Microsoft Account name > when the popup happens tap on "sync."
If it syncs, try your Backup again...
If it does not:
Make sure your date and time are correct
Try turning off any limits in Data Sense
Reboot
Try and sync your Microsoft Account again... If it doesn't sync, get back to us here for more help. And please remember we are just fellow travels here, not your OEM.