As in "Tal don't speak English."? That's ungrammatical. In third person singular you can say "does not" or "doesn't", in this particular context, I wouldn't be surprised if "can't" would be accepted. "don't" is for every other person and number. "isn't speaking" should work too. Remember I do, you do, he/she/it does, we do, you do, they do. Negation doesn't change that.