I want to update my Windows Phone from 8 to 8.1 but it takes forever to download. I have waited for it to download for three days but still no update takes place.
I haven't used the Device Recovery Tool in a while, but try downloading it and see if it allows you to update the phone to 8.1.
There is a good chance that it will wipe your phone if it does do the upgrade, so make sure you've backed up all of your data before you start.
https://support.microsoft.com/en-us/help/12379/windows-10-mobile-device-recovery-tool-faq
