if you don't know proper way and if possible for you go to service centre they charge some amount but safe way or go to nearby stores who is expert in this and get from them
Yes, you can flash your stock firmware through odin, go search for concern device firmware and download it and if possible latest odin.
-Else try flashing Twrp and then wipe everything and then process it through odin followed by firmware.
and if can't do both get in touch with nearest service center as they will provide latest software of the device published they will charge very decent amount and you can enjoy your device with peace.
