* **When they did not find him** - "When Mary and Joseph did not find Jesus"
* **It came about that** - This phrase is used here to mark an important event in the story. If your language has a way for doing this, you could consider using it here.
* **in the temple** - This could be translated as "in the temple courtyard" or "at the temple."
* **in the middle of** - This does not mean the exact center. Rather, it means "among" or "together with" or "in the midst of" (UDB).
* **the teachers** - "the religious teachers" or "those who taught people about God"
* **at his understanding** - This could be translated as "at how much he understood" or "that he understood so much about God."
* **his answers** - This could also be translated as "at how well he answered them" or "that he answered their questions so well."