YOU SAID:

i once went to the mall and falled down the stairs

INTO JAPANESE

私は一度モールに行って階段を落ちた

BACK INTO ENGLISH

I went to the mall once and fell down the stairs.

INTO JAPANESE

私は一度モールに行き、階段から落ちました。

BACK INTO ENGLISH

I went to the mall once and fell down the stairs.