You can't bypass that. It's in place to protect the original owner in case it was lost or stolen. You'll need to reach out to the seller to have them remove the device from iCloud.com/find if they are the original owner. Or get your money back because the device is possibly lost or stolen.
Apple does this to protect their customers. There's no way around it. Apple will remove an activation lock with only the original receipt (proof of purchase) from either an authorized reseller or Apple directly.
If you can get in touch with the seller, I'd just want my money back.
How to remove Activation Lock - Apple Support
Activation Lock for iPhone, iPad, and iPod touch - Apple Support