RaceChrono follows the language settings on your phone (See “Settings > General > Language & Region”). It will use the first language supported language in the “Preferred language order” setting. If none of the selected languages are supported, then English will be used.
So, if the app comes up with some “random” language, that is not what your phone is set to, but also not English, then you have this language in your “Preferred language order” setting. To fix this, remove any language from the list, that you do not want see your apps to appear in.