Flashing same rom over the already installed one?
It's not a guarantee that the phone will be back to normal (probably you have tripped Knox) but yes it should not be any problems flashing an original ROM over the one you have.
If the system says "Official" when reflashed it should be able to receive updates from Samsung when they are available.

Just remember to empty the cache and in worst case (if the flash does not work as intended) try and reflash with "Re-partition" (though you will probably need the partition file for that then).

Good luck
/Jonas