YOU SAID:

One time I fell down the stairs and farted.

INTO JAPANESE

一度私は階段の下に落ちて、怒った。

BACK INTO ENGLISH

Once I fell under the stairs, I got angry.

INTO JAPANESE

私が階段の下に落ちたら、私は怒った。

BACK INTO ENGLISH

I felt angry when I fell under the stairs.

INTO JAPANESE

私が階段の下に落ちたとき、私は怒っていた。

BACK INTO ENGLISH

I was angry when I fell under the stairs.

INTO JAPANESE

私が階段の下に落ちたとき、私は怒っていた。

BACK INTO ENGLISH

I was angry when I fell under the stairs.