I've only included the items that required correction. My changes are indicated in purple.
3. How has the question been answered?
It’s been answered by hearing soft and sweet voices of the children.
It's been answered by the sound of the soft and sweet voices of the children.
4. What does the poet mean by saying that the children open the windows that look to the east?
He means that children are the source of brightness and light in the world. It’s children that cause to make the sun rise and show its brightness to the world.
It's children that make the sun rise and show its brightness to the world.
6. Why does he compare them so?
He compares them, because children’s thoughts as innocent and nonchalant as the singing birds which in dawn soaring carelessly in the sky give a beautiful picture of tranquility.
He compares them because children's thoughts are as innocent and nonchalant as the singing birds, which soar carelessly in the sky at dawn and give a beautiful picture of tranquility.
7. How can the birds and the sunshine be in the hearts of the children? What does the poet mean?
He means children are generally carefree like the birds which away from the cares in the world drone soft and mellow tunes gliding high in the sky. Children speak their hearts, and their hearts are as pure and radiant as the Sunshine.
He means children are generally carefree, like the birds which glide high in the sky, away from the cares in the world, droning soft and mellow tunes.
8. The poet says that the children are thinking of the brooks while he is thinking of autumn. What does this mean?
The poet says so, because he has grown old and feeble, and his life is about to end like a plant that gets dried out in Autumn, while the children are young, energetic and lively like running brooks.
11. How are the children different from the poet?
The children differ the poet in many aspects. Their thoughts are as innocent and carefree as the singing birds, which carelessly drone soft and sweet tunes in dawn. (see above correction)
In their hearts "are the birds and the sunshine”, and in their thoughts "the brooklet's flow”, while the poet is seized in the hands of trouble, and in his heart and thoughts “is the wind of Autumn, and the first fall of the snow.” And most importantly, he has grown old and fragile, it has taken almost all his lifetime to make his fortune, whereas the children are young and bouncy, and it’s just the beginning of their journey.