here is the firmware for DOOGEE DG500
Flash Tool Download Link:SP-Flash-TOOL-V3.
Please drive it before you reflash it. You can use the driver tools which all the MTK 65XX can be used.There is the download address: MTK 65XX Driver (Password: geekbuying.com).
Then,choose the files in Star U89 firmware package as follows:
3.Click UPGRADE here:
4.Connect your phone with PC, then wait about two minutes until you see the green circle.