Maybe contact the author of another language mod like ruESO.
If I'm right you need to use a tool like the "Black Book Browser" and extract the eso source files.
In there should be all the strings of the game you need to translate to hungarian then.
And then you need somehow "inject" those custom language files to the game source code again.
Maybe you aloso need other fonts.
-> This are the parts where I do not know how to do this and you should ask other addon authors (like the mentioned ruESO) for assistance please.