YOU SAID:

If I don't have to do something, I won't, but if I have to, I'll do it quickly.

INTO JAPANESE

やる必要がないときはやらないけど、やらなければいけないときはすぐにやります。

BACK INTO ENGLISH

I don't do it when I don't have to do it, but when I have to do it, I do it right away.

INTO JAPANESE

やらなくていい時はやらないけど、やらなきゃいけない時はすぐやる。

BACK INTO ENGLISH

I don't do it when I don't have to do it, but when I have to do it, I do it right away.