YOU SAID:

once upon a time the end I guess

INTO JAPANESE

むかしむかし、終わりだと思います

BACK INTO ENGLISH

Once upon a time I think it's over

INTO JAPANESE

いつかは終わったと思う

BACK INTO ENGLISH

i think it's over someday

INTO JAPANESE

いつかは終わると思う

BACK INTO ENGLISH

i think it will end someday

INTO JAPANESE

いつか終わると思う

BACK INTO ENGLISH

i think it will end someday