You Can Also Try Rooting Method if you Need.
If You not yet Try Auto Method then Try Auto Method-Samsung Galaxy J7 SM-J700F 6.0.1 Marshmallow OTA Update.
Download Samsung USB driver.
Download Odin.
Download Firmware For Samsung Galaxy J7 SM-J700F 6.0.1 Marshmallow Update Firmware.
Install the Samsung USB Driver in your PC.
Extract the Odin Files in your PC.
Copy the Unikernel files in your PC.
Switch off your Mobile.Enter into Download mode->Volume Down+Home+Power Buttons.
After entering into Download Mode it will say Warning Press Volume Up button to continue.
Connect Your Mobile With PC via USB Cable.
Launch Odin Application.It Will Show the message added.If you did not get this message Repeat the above steps.
After Getting Added Message Select PDA Button then Browse for the Firmware file Select it.Tick the Auto reboot.
Press Start wait for the tasks to complete.It may enter into Recovery mode to add the SuperSu permissions.Reboot again.