Who I can contact to the previous owner of watch

No one can help you reach the owner whose ID is locked to the watch. Apple will NOT help you. We cannot help you.

As Rudegar correctly suggests, if you bought a used Apple Watch, which is locked to a previous owner, you've most assuredly been scammed and wasted your money on a useless device you can never use.

If you did buy a used Apple Watch, see if you can get your money back. If you can't get your money back, recycle the watch responsibly as it is utterly useless and there is no one who can help you.

Read this too --> The All Too Common SAD Reality of Buying … - Apple Community

sorry no, you got scammed

activation lock is not a thing on the ipad it's a theft protection on apples servers

it needs to be removed

About Activation Lock on your

Apple Watch - Apple Support

if you don't know your appleID password If you have

forgotten your Apple ID

password – Apple Support (UK)

then you will need the assistance of apple Activation Lock - Support

(apple.com)

and or

 Apple Support

And or

 Contact - Official Apple Support

and or

Genius Bar Reservation and Apple

Support Options - Apple