It's might be too difficult to add new languages with the way that the game is set up. Try "XUnity AutoTranslator", which is a really great tool and I use it all the time to play Unity games in languages I don't know. It can be configured to work with multiple different translation services, so you should be able to find one that works well for you. Most of the games that I'm making are focused more on gameplay rather than story, so don't worry if you can't understand the plot.