How to respond invited?

if we want to go to the invitation then just say, okay if I have time I will definitely come. but if you do not want to come then just say I apologize coincidentally your event coincides with one of my events once again I apologize I can not come.
Artinya:
kalau kita mau untuk mendatangi undangan itu maka katakan saja,baiklah nanti kalau saya ada waktu pasti saya akan datang.namun bila tidak ingin datang maka katakan saja saya mohon maaf kebetulan acara anda bertepatan dengan salah satu acara saya sekali lagi saya mohon maaf saya tidak bisa datang.

Ini paling banyak jika ada kata RSVP (Répondez s'il vous plaît) yang memiliki inti merespon ketika mendapatkan surat. Respon dapat dibagi dua, respon bisa datang atau tidak bisa datang (pada umumnya)
Respond invited juga tergantung dalam konteks apa terlebih dahulu, paling banyak dalam surat undangan ulang tahun.
Contoh:
Bisa datang:
Hi, ... (nama). I got your mail. Well, I could go for celebrating your birthday. I will be there as fast as a bullet and as clear as a whistle. Just prepare yourself, because ... (nama Anda) will celebrating your birthday. Just you wait and see. 

Tidak bisa datang:
Hello, ... (nama). I got your mail. I'm terribly sorry to tell you this information, but I could not go anywhere on that day. My sister is also throwing a birthday party, and my parents forced me to not go anywhere outside my house. I know that you are my friend, but, I cannot join you on your birthday. Hey, at least, there will be some people who will join in your birthday party, right??? Well, haappy birthday, ... (name). Please note that I might join you. Just you wait. Like Hamilton, the musical, 'there's a million thing I haven't done, just you wait.' Ok, bye.