YOU SAID:

cross that bridge when I come to it

INTO JAPANESE

私がそれに来るときその橋を渡る

BACK INTO ENGLISH

Cross the bridge when I come to it

INTO JAPANESE

橋に着いたら橋を渡る

BACK INTO ENGLISH

When you reach the bridge, cross the bridge

INTO JAPANESE

橋に着いたら橋を渡ります

BACK INTO ENGLISH

When you reach the bridge, cross the bridge