Letter of apology

Hello,

a friend of mine had to write a letter of apology for his course in Business English. He wrote the following letter of apology. The teacher crossed nearly all of his words out. Is the letter grammatically an absolutely nonsense or what did he wrong?

Thanks for your answers.

Dear Mr Smith,

I am writing to apologize for missing our appointment from yesterday afternoon.

I know it was a very important appointment. However, let me try to explain why I missed our appointment. You certainly know my colleague Max. I had a meeting with him about the alteration of a contract you had sent me by email yesterday morning. Suddenly, Max gasped for air, and fell down from his office chair. He got a heart attack, and was immediately taken to hospital. I accompanied him in the ambulance. There he was examined at once. Fortunately, he only had a mild heart attack. He is now well again.

Once again, I apologize for missing our appointment.

Therefore, please let us arrange a new appointment. I propose we meet again next week. We have no time to lose. I am going to suggest you four different dates. Please, choose between the following propositions: Monday 27 July at 3pm, Wednesday 29 July at 9am or 2pm or last Thursday at 11am.

If you have further questions, please do not hesitate to contact me at Email Removed or on 12345.

I look forward to hearing from you soon.

Yours sincerely
Robert Mueller