This firmware package for Gionee S5.5 (GN9000) is meant for easy flashing via SP Flashtool.
Download from the link below and follow the flashing instructions after downloading to learn how to flash the stock ROM and where to download SP Flashtool if you don’t already have it.
Gionee S5.5 (GN9000) – Download
How to flash firmware
For SP Flashtool download and flashing instructions, follow this link.