What do you think about the fact that my boyfriend learned a language behind my back and humiliated me in front of my family? I'm really mad at him about it, too.
How did this family scene play out?
I was embarrassed, but I didn't show it.
Your partner is impressive to be learning new things, but he shouldn't use such knowledge for petty things like this. You shouldn't humiliate others in general, much less your partner in front of her family.
If you saw how he acted, you'd be mad, too.
It's possible he isn't even conscious of his behavior. You should sit down and explain how his behavior affected you.