Hi, your idea is actually good, and I'm pretty sure Japanese people understand what you want to tell. Here are some tips, hope they are helpful. 'I am studying Japanese in my spare time.' 「時間がある時に僕は日本語を勉強しています。」Jikan ga arutoki ni boku ha nihongo o benkyoshiteimasu ◎「時間のある時に」in my spare time Unlike English, we don't usually say the possessive pronoun especially when the subject in the sentence owns it. So you don't have to say "僕の" =my 「時間のある時に」is a neater way to say than 「暇な時間に」. 「暇な」sounds a bit casual. ◎「僕は日本語を勉強しています」I am studying Japanese. 「勉強中（です）」means the present progressive, so it means you are studying it right now. I guess you mean that you are in the habit of studying Japanese in your spare time, so I would use 「勉強しています」form which usually means "the habit" of doing something. I always welcome your further questions and your feedback about my English. I want to brush up my English more.