You bought an item.
There was a problem and you asked the seller if you could return it.
The seller agreed to the return.
You then left on a trip before returning the item.
You told the seller about your trip.
The seller agreed to extend the time for the return.
EBay has been reminding you to return the item.
Did you also open an eBay dispute? This is the only way eBay would know about the problem.
EBay has standards for opening and closing disputes.
If you cannot show that the item was returned in the time eBay allows, eBay will not help you with the refund.
However.
It sounds as if the seller is willing to wait. The eBay messages are automatic, not personal.
When you return, upgrade your shipping service to get the item to the seller faster. If it is still too late for eBay you will lose the Dispute, but that is not important if your seller is still willing to refund you.
If the seller refunds you when tracking shows he has the item back, all is well. Leave positive feedback. "Thank you for your help with this.' for example.
At the same time leave Five Star Ratings for the seller. He has shown great patience.
If the description was bad, but the rest of the transaction was good, leave NO rating for Item Description.
If the seller refuses the refund when the item arrives, and eBay has closed the Dispute, you can still go to the credit card you really paid with, (Paypal is a useful mediator), phone their 1-800 number and ask about a chargeback. The clerk will need dates, transaction numbers, payments, and currency information to complete a refund.
And if none of this works, try selling the item locally for cash on Kijiji or Craigslist.
This is complicated and long. If you find it difficult, use Google Translate to change it to your own language.