That's not correct Keira..."I will need it in my course in the english language" does not sound right. You would say "I will need it FOR my English language course"

If you really want to use "need", the full sentence would be...

"I want to learn English because I will need it for my English Language course."

Asahi you were not so far off with your initial effort. You could say

"I want to learn English because I will be studying the English Language"

However the whole sentence could be put in a slightly better way.You want to learn English because it will help you in your studies. A better way to articulate what you are trying to say would be

"I want to learn English because it will help me in my English Language studies"

First notebook entry: Introducing myself

I want to learn english because I will study need it in my course in the english language.