YOU SAID:

I WAs once with a donkey

INTO JAPANESE

私はかつてロバと一緒でした

BACK INTO ENGLISH

I used to be with a donkey

INTO JAPANESE

私はロバと一緒にいました

BACK INTO ENGLISH

I was with a donkey

INTO JAPANESE

私はロバと一緒でした

BACK INTO ENGLISH

I was with a donkey