改进题：My brother stayed in Hong Kong for five months, during which time l often wrote him letters.

译文：我哥哥经常收到我写的信在香港呆的五个月里。

改进题：My brother stayed in Hong Kong for five months, during which time l often wrote him letters.

译文：我哥哥经常收到我写的信在香港呆的五个月里。

改进的译文：我哥哥在香港呆了五个月，期间我经常给他写信。