'The dress, a generious gift' - FCE Writing task thank you letter

Topic: Write a letter to thank someone for a birthday present which has come just at the right time and pleases you very much.
Dear Nga,
I would like to thank you for the generous gift. I am so glad that you spent time choosing such a wonderful gift for me. The dress you bought is truly one of the most lovely gifts I have ever received. And the most wonderful thing is that it has just come this morning, on this special day. What a nice surprised!

It is difficult for me to find the words to express my gratitude. The dress is really a perfect thing. Its style and colour suit me well. I truly fell in love with it just as I opened it.

Once again, thank you for the wonderful present. It really made my birthday a special and happy one.
Yours sincerely,
Please help me check this task! Editing is highly appreciated!

"AndT he most wonderful thing is that it has just ca me this morning, on this special day. What a nice surprised !"
* What is striked out I would strongly recommend getting rid of.
*What's in red is corrections.

I feel like you over use the word "wonderful" , you should explain what your "special day" was.

I know a Thank You letter is not ment to be as formal as most writing pieces and may not need as much detail, I do feel that it does lack detail.

This piece has potential to being a good writing task / Thank you letter though, good luck !

"Special day" means my birthday. Thank you so much for your suggestion and correction, Cecilia!