You need to accept the return and provide the buyer with a label.
You will need to refund in full when you get the item back.
You only provided 2 photos - if there were any specific issues with the laptop, you should have added them to the description and given details.
A used item may 'have some signs of cosmetic wear' but that does not cover an external defect not mentioned in the listing.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)