please i have a second hand iphone but i cannot find the owner

I am guessing that the phone is locked to the previous owner by Activation Lock. There is no way to defeat this lock without the credentials of the previous owner. We cannot help you and Apple will not help. Activation Lock is a theft prevention feature that cannot be circumvented. If you can, return the phone and get your money back. The phone is useless for you.

Did you purchase this iPhone?

• Yes. If you cannot get the owner to terminate the Activation Lock for you, the iPhone will remain useless. It was likely stolen before you purchased it. Get a refund if possible. Turn off Find My iPhone Activation Lock - Apple Support
• No. The iPhone is not yours. Turn it over to the authorities.