IELTS preparation. Apologize Letter of Apology. ~25min (Hard theme for me)

Dear Mr. Black,

I would like to apologize for the inconvenience but I need to inform you that I can't attend the course "Leadership skills: level 2" on next week. It is very important for my personal development. I was planning to apply to a management position next year and this course certificate would verify complete (?) my qualification. I'm really upset that I didn't know about the dates of this course before.

It is likely I will pity regret this missed possibility opportunity, but I have already booked my vacation and have bought tickets in with the travel agency. If I return the tickets I will have to pay an 80% penalty and upset my child who is has been dreaming about this trip.

I heard that this course would will be arranged held again at the end of the year. I would be very grateful if I could attend that session instead.
May I apologize again for that this inconvenience and ask you to include me to in the list of listeners of the course at the end of the year.

I'm looking forward to hearing from you.

Yours faithfully,
Mark Ricard