Are You Saying That All Human Languages Have a Universal Grammar?

If all we get are their messages, it would be impossible for us to translate t. We don't have a context for what their lives are like and what they might mean exactly. So if we could spend some time with the aliens and develop some common context, then we could have the framework for developing some sort of effective, but imperfect translation. But i think then er you would be committed to some fairly controversial views in the philosophy of language.