How to add more language to the Android system

I need help I have Meizu C9, which has Android 8.1 and several languages ​​on these devices, but no Hebrew in the settings menu, but Hebrew on the phone.
If I use a more local app and select Hebrew, the device language will be changed, but after restarting, the phone language will change back to English.
I want to know which APK contains the list of languages ​​so that I can edit this APK and add the Hebrew language. In Samsung I know how it works, no problem, but in this Meizu I do not thank a body that helps me