We are to write a phase autobiography. English is my second language. Could you just point out some obvious mistakes or awkwardness? These are just segments of my imperfect essay that I am not quite confident to show.

Even when his raven hair suddenly turned so white, and had to greet me on his smelly, maroon sofa, I never thought I would have to lose his awkward laugh, or let Grandma receive the traditional curtseys alone on New Year¡¯s Days.
(Do you think this sentence is too long?)

Noticing my white princess dress rustling as I walk, I quickened my steps toward Grandpa.
(Is the verb 'walk' wrong in the sentence?)

There were hundreds of dragonflies spotting the clear March sky that almost shielded the sunlight. It was just that little portion of the sky above the house they chose to linger.
(Is the second sentence wrong? Teacher drew a line across it.)

Even when his raven hair suddenly turned so white, and he had to greet me on his smelly, maroon sofa, I never thought I would have to<~~delete "have to" lose his awkward laugh,<~~delete comma or let Grandma receive the traditional curtseys alone on New Year's Day.

(Do you think this sentence is too long?) You could probably break it up at "let Grandma..." -- make a separate sentence there.

Noticing my white princess dress rustling as I walk<~~need paste tense here, to match the past tense main verb "quickened", I quickened my steps toward Grandpa.
(Is the verb 'walk' wrong in the sentence?)

There were hundreds of dragonflies spotting the clear March sky that almost shielded the sunlight. It was just that little portion of the sky above the house they chose to linger.
(Is the second sentence wrong? Teacher drew a line across it.)
My question about the second sentence -- what is "it"??

Sorry -- should be "past tense" (not "paste")!!!

Overall, your writing is quite good, and there are only a few minor suggestions and clarifications that I can offer to improve the flow and clarity of your text:

1. Even when his raven hair suddenly turned so white, and he had to greet me on his smelly, maroon sofa, I never thought I would have to lose his awkward laugh or let Grandma receive the traditional curtseys alone on New Year's Days.
- The sentence length is fine, but to improve clarity, it's better to use "he" instead of "had to" to indicate that your grandfather had to greet you on the sofa.

2. "Noticing my white princess dress rustling as I walk, I quickened my steps toward Grandpa."
- The verb "walk" is not wrong, but if you want to make it more clear that you were already walking, you can say "as I was walking."

3. "There were hundreds of dragonflies spotting the clear March sky that almost shielded the sunlight. It was just that little portion of the sky above the house they chose to linger."
- The second sentence is slightly unclear. Instead of saying "it was just that little portion of the sky above the house they chose to linger," you can say "they chose to linger only in that small portion of the sky above the house."

Remember, these are just suggestions to enhance the clarity and flow of your writing. Keep up the great work and don't be afraid to seek feedback from others to further improve your essay.