Hi Konoi, I guess you are playing on Windows right? The default language is English, but it seems that this feature is working only on mobile devices, Mac and Linux. We have discovered this issue recently and we are working to fix it, sorry about that.
About the full screen, I would recommend playing like that, but I will release the option to play on window mode and choose the ratio.
Again, sorry for the inconvenience, we will upload an updated Windows version that fixes these issues as soon as possible.