If you're sending the message to a friend around your age you can say; 수요일 생일 파티(는) 잘 했니? 수요일 생일 파티(는) 재미있었어?
-Did you enjoy your birthday party on Wed?
(Can you read Korea characters here???)
Korean translations are slightly different from your original sentence, but those are more natural way to say.
If you want to add "my best wishes" at the end of the letter you can say; 잘 있어. or 안녕.
(There are many ways that you can end a letter or email, but these are most common and simplest way to say.)
But if the recipient is older than you, you have to say differently.
"Whodunit" sent me a private message that someone is asking for help in Korean, and just now I read the message. I think it's too late to be helpful to you, isn't it?