The v3.7 update focuses on delivering a "next-generation" experience on hardware limited by 1GB of RAM and an Exynos 3475 chipset.
To install Next Gen OS v3.7, you must have a custom recovery like installed on your device. next gen os v3.7 for j200g
Boot into TWRP recovery and perform a "Wipe" of the System, Data, Cache, and Dalvik Cache . The v3