How do I remove activation lock on my iPhone?

Activation Lock is intended as a theft deterrent, and is intentionally difficult to bypass.

We can’t help, and absent proof sufficient to convince Apple, Apple won’t help.

You’ll need the assistance of the person with the Apple ID holding that lock, or recovery of your own forgotten Apple ID if that’s holding the lock, convincing proof of ownership, or the assistance of the seller if they haven’t disappeared.

And these cases often involve a seller that has disappeared, which means this device is probably lost or stolen, and you got scammed

The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community