YOU SAID:

I have come down with a case of fast bottom

INTO JAPANESE

私は高速の下のケースに下がってきた

BACK INTO ENGLISH

I fell in a case under the high speed

INTO JAPANESE

私は高速の下の場合に落ちた

BACK INTO ENGLISH

I fell down fast if

INTO JAPANESE

場合は、高速から落ちました

BACK INTO ENGLISH

If you fell from a high speed

INTO JAPANESE

高速から下落した場合

BACK INTO ENGLISH

If you fell from a high speed