Where do you want to change the language?

At the rail planner app

As far as I know the app is only available in English. 

The app is also available in German and Spanish and maybe also in a few other languages. Unfortunately, the app does not have an option to change the language from within the app. Instead, it looks at the languages configured in the operating system and then from that list it takes the first one it knows. If the app doesn’t know any of the configured languages, then it defaults to English.

For example: I have my phone set up with Dutch at the top of the configured languages and then normally English, German and French. The rail planner app does not know Dutch and will then show up in English. If however, I move German to the second spot in the language list, then the app will show up in German the next time I launch it.