The app is written in eleven Indian languages besides English, and not as a layer on top. Every line of text a person can see goes through the same translation lookup, so a screen cannot quietly fall back to English because somebody forgot it.
The part that is only discipline
Every piece of text is wrapped at the point it is written, which means a line that was never translated is a line a script can find. Three of them run over the whole codebase: one that lists what is missing, one that merges new lines in, and one that removes lines nothing uses any more.
That last one matters more than it sounds. A translation file that only ever grows becomes a file nobody trusts, full of strings for screens that no longer exist.
The parts that are hard
Error messages. They are written by the part of the app furthest from the person reading them, and they are the sentences that matter most when they appear. Anything a server refuses has to be translatable too, not just the screens.
Numbers, dates and money. Each language gets its own formatting, because a date that reads correctly in English can be ambiguous in translation.
Words we chose not to translate. Some are clearer left alone. A host is a host.
The part that is still not right
Urdu is written right to left, and it is the only one of the twelve that is. The layout handles that by describing positions as start and end rather than left and right, which flips correctly as a whole.
Where that breaks is any style still written as a physical left or right. There is no separate right-to-left stylesheet to catch it, so such a style lands on the wrong edge, and it does so only in Urdu — which means it is invisible to everyone not reading in Urdu, including us.
So there is a page asking people to report exactly that, and the reports are useful. This is the honest state of it: the structure is right, and individual corners of it are wrong until somebody says so.
What is not translated
The staff console. It is an internal tool, it is used by people who work here, and translating it would be work that helps nobody who buys or sells.
Questions people ask
How do I change my language?
In your settings. The app also starts in your phone's language on your first visit, if it is one of the twelve.
What if a translation is wrong?
Report it. A wrong translation of something that costs money is the most expensive kind of bug here, and the hardest for us to see.
Will there be more languages?
These are the most spoken ones. More means more to keep correct, and a stale translation is worse than none.
More: using Metzee in your language, reporting a translation mistake, when something is on the wrong side, eleven languages.