Надо сделать предложения более позитивным 1. Sorry ,I have no idea about it, as it’s not my responsibility. 2. I’m sorry to have kept you waiting. 3. We can only supply the goods after receipt of your payment. 4. I’m sorry I didn’t respond to you in time. I was too busy. 5. Your letter is not clear at all. I can’t understand it.

Well, i have an idea for this situation because it is my responsibility too.

Hope that i haven't kept you waiting for a long time.

We can supply the goods for free after your payment.

Sorry, i didn't respond you in time because i made this gift for you.

Your letter is not bad but i believe that you can write it better. Just don't give up!