Answering a customer before they change their mind
Most questions arrive before the order, not after, and most are the same three questions.
The three
"Is this the real size?" "Do you have it in another colour?" "When will it arrive?"
Answer the first two from the product in front of you. For the third, say what you know — when you will hand it to the courier — and nothing about what happens after that. A delivery date you invented is a refused parcel later.
Answer it once, then write it down
If you have answered the same question twice, it belongs in the description. The question will keep coming otherwise, and the customers who do not bother asking simply do not buy.
Saying no
"I do not have that" is a complete answer and a good one. Offer the nearest thing you do have, once. Do not offer to source something you are not sure you can get.
Speed over polish
A short reply today beats a careful one tomorrow.