>>90
>>91
Actually, you're both a little bit off.

It's more like:
英語を勉強しなければ英語で怒鳴らないなさい

「英語を勉強しませんなら」would be more like, "since you don't study English..." So, your sentence would translate to something like, "Since you don't study English, you don't shout in English."

Also, 〜下さい is more of a request than a command. If you want to give a polite command, you use 〜なさい.