Missing Czech Language,hidden language.. how to enable it ?

Hi! I have stock rom installed on my Note 4 Sprint but i cannot change language.. it looks like is avaible only English and few more languages,but i need enable permanently Czech Language.. every time when i try it change with some third party app it will be just to reboot.. after it is English back (and also,the Czech language is not completely everywhere.. for example is not in settings).. Does anyone know how to permanently change it ?