Thank you for suggestion

哼着他的曲 -> 唱着他的歌 -- I hesitated between the two choices. I picked up "哼着他的曲" to add change of the rhythm but "唱着他的歌" is more consistent with the rest of the poem and also sounds excessive repetition. The latter may be a better choice thinking about the overall effect.

那女孩子正在缝补洗浆 -＞ 在缝补洗浆的女孩 --I use the way to rhyme.

Thank you again.