[mothered]

One last question before I answer them. Do you think that in order to make me look more innocent it is better to send a more simplistic email first, like for example

"Hello,
I am replying to the email you sent me yesterday.
I returned the product I bought several months ago.
I don't understand what you are talking about and why you are coming to me today with these questions.
I wish you a good day.

And only then if they persist to send the previous mail, more detailed and argued? Or is it better to send directly the more complete one?

Initially, a simplistic reply yet addressing the matter effectively, Is a better approach - as per your message above.

If need be, you can go Into more detail accordingly.

Thanks again for your help you are saving me

It's my pleasure to be of help.