I downloaded the file from the torrent link. it was pretty fast. didnt take more than a couple of hours. I have saved the file under \ProgramData\Nokia\Packages\Products and i can see the file under " downloads" in NSU however i don't have a clue how to install it from here. When i open NSU it searches for firmware and shows me the old one only.
You need to download Nokia care suite first then follow these steps
Link to Nokia care suite
http://sdrv.ms/18jOceL
1. Launch Nokia Care Suite
2. Click the Product Support Tool for Store 5.0
3. Click File
4. Click Open Product
5. Choose RM-914 (Nokia Lumia 520)
6. On the bottom left click Programming
7. Click Recovery
8. You should see the firmware you downloaded and copied earlier under the Properties field.
9. Click Start
10. The software will check the package contents, it will fail to find the phone, and ask you to reboot and give you a button to click retry.
Phone Directions:
1. Plug the phone into your PC
2. Hold the Volume Down and the Power button, click RETRY on the Product Support Tools Window
3. After you feel a vibration in the phone immediately release the Volume Down and the Power button and hold the Volume up button.
4. Continue to hold the volume up button, you will see the software say "Rebooting"
5. After about 15 seconds you will see a top NOKIA logo and the software will start flashing the phone.