YOU SAID:

an elephant was walking when it saw a very big bird fly over head.

INTO JAPANESE

非常に大きな鳥が頭上を飛んでいるのを見たとき、象が歩いていました。

BACK INTO ENGLISH

An elephant was walking when I saw a very large bird flying overhead.

INTO JAPANESE

非常に大きな鳥が頭上を飛んでいるのを見たとき、象が歩いていました。

BACK INTO ENGLISH

An elephant was walking when I saw a very large bird flying overhead.