YOU SAID:

you can't ride two horses with one bottom

INTO JAPANESE

1 つ下の 2 頭の馬を乗ることはできません。

BACK INTO ENGLISH

You can't ride two horses down one.

INTO JAPANESE

1 つ下の 2 頭の馬に乗ることはできません。

BACK INTO ENGLISH

You can't ride two horses down one.