Looking for Advice or Guide on How Best to Translate App

I see quite a few apps out there handling Translation quite well, but very little in terms of a guide or walk through on best way to translate an app.
Is it using Google Translate and App Script?
Is it double, triple or quadrupal rows with translations and giving a choice?

I have a question at signup which allows users to select a language they prefer but other than that having a difficult time figuring out the best way to translate across the app. Are there any examples out there that I can follow?
Thanks so much…