You paid for it, but you returned it?
You are covered by Paypal for 180 days from Payment.
You will need the tracking number on the returned shipment to prove the seller had it back.
You may also be covered by the credit card I hope you use to back up your Paypal account. Their policies vary.
So.
Keep an eye on the tracking for your returned parcel.
When it is back in France, open an Item Not As Described dispute in the PP Resolution Centre under Tools at the top of your PP account page.
I mistakenly shipped the return by a slow method and it took 6 weeks for the package to reach the seller. In the meantime, the seller became impatient
This was your mistake. Grownups take responsibility for their mistakes. It was not the fault of eBay or Paypal that you made this mistake.
Experienced eBayers warn newbies not to use Surface shipping exactly because it does take so long.