Suppose you are developing a project, like a video game, and you would want (or need) to translate and localize it to another language, one that you have no understanding of whatsoever. How exactly would you assure the quality of the translation?
(If you are wondering why I'm using "translation and localization", and what the difference is, it's this: Translating text from one language to another is to reflect as accurately as possible the things that were said in the original language, with as few changes as possible. Localizing the text, however, requires more than simply translating it. Pure translations are more proper for things like legal documents, documentaries, and even some forms of fiction. However, this is not always suitable for all forms of fiction. The most typical thing requiring localization (rather than blind translation) are jokes, puns, wordplay and certain things that are extremely culture-specific in the original language, and wouldn't translate well into the target language. As a rule of thumb, if a literal translation would require a footnote to explain the reader what it means in the original language, this is often a sign that it requires localization, especially if such footnotes cannot be used or would be awkward or unsuitable in the work or its context.)
So, going back to the original question, if you need a translation/localization of your work into a language you don't understand, how exactly can you make sure of the quality of that translation?
You can ask a friend or somebody else on the internet to do the translation for you. Or, in extreme cases, hire a professional translator. But even in this latter case (not to talk about the former ones), how can you assure quality?
Even professional translator may do a poor job at translating, and especially localizing, your work because they might not have a good picture of what you want (even if you try to explain it to them). Also, being professional (ie. doing it for money) is unfortunately not a guarantee of quality.
If you were commissioning art, there would be no problem. The artist creates the images you request, and you can easily check them to see if they match your vision, and request fixes if they don't. But language is not that easy, if you don't understand it.
One thing you could do is to ask for an independent second opinion. In other words, give the translation to someone else who understands the language well (preferably a native speaker) and ask them what they think about it. This probably does indeed help quite a lot, but still you are relying on other people to assure the quality of your own creation, you yourself being unable to do so. Neither of those other people might understand perfectly what it is that you want, and might let grave mistakes pass, because they don't understand them as mistakes. Or perhaps the tone is just wrong, or some form of localization is poor, or perhaps the translator made a literal translation of something that should have been localized... or a myriad of other things.
This is a hard problem, especially for small-scale developers who work solo or with very small teams.