Nokia Lumia 520 flash file has been released and download links are available for download on different websites. You can flash your phone by using below flash files. Nokia lumia 520 rm-915 firmware required for do software or update old software.To flash your mobile first take a backup of your contacts, messages or data which store in your mobile gallery. After flashing mobile will be restored in its original settings and data will be removed. You can use different tools or boxes for flashing phones.
Nokia Lumia 520 Flash File/Firmware (Google Drive Link)