How to unlock iPhone 11 pro max actvation lock?

If you see an "iPhone Locked To Owner" message:

Take it back to the person from whom you received it. Get them to do the things in this support article or ask for a refund --> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support There is no way of discovering the owner of a device unless they left a message to display on the device when it is turned on.

Unless you have the account information that set the lock, or the original receipt from Apple, you cannot remove the lock; recycle the device. Read this article about how to remove Activation Lock --> How to remove Activation Lock - Apple Support

From the very bottom of Apple Trade In - Apple :

"Does Apple offer recycling?

Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."

Your ONLY option is to get the 1st owner to perform these steps:

How to remove Activation Lock - Apple Support

Without his/her cooperation, the iPhone will never function for you.