Hi, thanks for your suggestion, but i already did by trial and error. But still some apps and some notification remained to korean(or chinese) language. That's why i asked here to change whole firmware. But as @nokiamodeln91 posted above, it cant be possible.
If an apk doesn't have the language resources it will stay with the standard - here Korean.
I made an "all-language" custom rom before where I added missing languages to all apk in a Samsung TW rom. This is an ugly and boring work. So no chance without this work to get more of your wanted language on this device.