YOU SAID:

if it slaps on his knee when he walks! I shall listen when he talks

INTO JAPANESE

彼が歩くとき、それは彼の膝の上に平手打ちした場合!彼が話すとき、私は耳を傾けるだろう

BACK INTO ENGLISH

If it slapped on his knee when he walked! I will listen when he speaks

INTO JAPANESE

彼は倒れたときにひざを痛めた。

BACK INTO ENGLISH

He hurt his knee when he fell.

INTO JAPANESE

彼は倒れたときにひざを痛めた。

BACK INTO ENGLISH

He hurt his knee when he fell.