How do you say this in Japanese: "One day in the future, I want to own and operate my own business in Japan"?

Question:

please no translation sites.
also, my teacher highlighted "ー" in "ー年間". any idea why this would be marked at being wrong?
これまで日本語をー年間べんきょうしてきました

Answer:

I think this is simple.
「いつか日本で自分の会社を持ちたいです」

"一" is different with "ー".
"一" means the number of one.
"ー" is the character of cho-onpu which requires to keep vowel pronunciation sounding a few moments.