It was great hearing from you. I'm sorry I haven't written in so long.
In your letter, you tell me about your costume party. I never had such an interesting tradition in my school, for which I can make costume. If I had, I would fancy wearing a pirate costume. I would rather make the costume myself because it is a good way to create your own unique costume. In general, I think costume parties are great opportunities to have fun with friends.
By the way, can you tell me more about the museum? What historic period did your museum trip focus on? Do you like visiting museums?
I should go now since I have homework to do. Write back soon!
With love,
(Insert your name)
~
The corrections aren't perfect as I was trying to retain your wording of it and make the letter sound more conversational ad casual. Some grammatical errors exist in my correction. I'm sorry I cannot explain my corrections...my English isn't good enough for me to explain my changes. =[ If you do have any questions though, let me know, and I will try my best to explain!