We can't help you. Apple won't help you. The ONLY person who CAN help you is the person who gave you the watch. If you can't contact them, they won't be able to help you, so the watch is utterly, totally useless to you. There is NO WAY for you to remove Activation Lock. Only they can.
It also doesn't matter whether it was given to you or you paid for it. Without the owner who locked the watch removing it from their account, there is no one on the planet except them who can help you.
Recycle the watch responsibly unless you want to strap a useless watch to your wrist and wear it for show.
While you say you didn't pay for the watch, this user tip I wrote still applies, so please read it --> https://discussions.apple.com/docs/DOC-250001038