[ Flynn's sheer enthusiasm almost gets an actual smile out of Castiel. It doesn't quite, because human facial expressions are still something he doesn't have the best grasp on preforming himself just yet, but it's still pretty clear that he's pleased, at least.

[ He does switch back to English for the time being, though. ]

I'm not much of a teacher, but you're very good for having had to reconstruct the entire language by yourself. I think you'll mostly want to know more common words and grammar.