Why is he so arrogant and not to nice to me?

I read all your details, but it's just weird to me. If I were in your place, I really wouldn't care what my spouse's sibling said about me. The real problem here is that your HUSBAND laughs at you while excluding you from conversation by speaking in another language. And that is what you should address with your husband, HIS behavior, and you should have this discussion before his brother arrives.

He is arrogant coz he knows you take offense with it and he enjoys it. Instead change your perspective and don’t take any notice of his arrogance, plus give a piece of your take to your husband, the way he will handle it will enlighten you about him too, coz he might be the real problem than what you actually see.

Worrying about your husband’s brother is quite a stretch, coz next you will start worrying about the brother’s cat and dog too not to mention his neighbors too. You seem to stretch your chain of worries unnecessarily. If I were you, I would worry about your husband alone, the rest? give yourself some piece. His arrogance has no any other value other than the one you assign it.

if you husband is laughing at how u look with his brother or whoever he is the one who is disrespecting u and he is the one whom u should address the issue