writing a letter

General comment: remember that the first letter in each sentence is uppercase, and that "I" is uppercase wherever it occurs. :)

"Response" is the noun (اسم), "to respond" is the verb (فعل).

You could say "told him about my problem" or "explained my problem to him".

"absent" in this context is correct but a bit formal. To say "he was out" is more natural.

When you have "to" followed by a verb, the verb is in infinitive (مصدر): to write

"I really was worried" is also correct, but "I was really worried" is more common.

There are many ways to say "was worried about is it write politely". I gave one suggestion above, but you could also say "was worried about it being written politely" or just "was worried about it being polite".

These are tricky rules. You are doing well!

یونس

Writing a Letter

Last Friday I received an invitation letter from my supervisor. I read it and I thought that some parts of it needed to be changed, but I didn't know how do that. It was so difficult for me to rewrite it in English. First I called one of my friends and told my problem to him, but he couldn't help me. After that I went to my adviser's office, but he was unfortunately absent. Finally I decided to respond to it myself. It took two days for me to write this letter. At that time I was really worried about whether  it was written politely. Today I sent it and she responded to it immediately. She will resend another invitation letter tomorrow.

-Most of the corrections were capitalization issues. You always need to capitalize the personal pronoun 'I' and the first letter in a sentence.