How do I know if my iPhone 15 Pro Max is original?

The best way to check your phone is to enter the serial number here: Check Your Service and Support Coverage - Apple Support since you can no longer contact the person you got this from, you may have a stolen phone. You may need to recycle it and get a phone you can use.

Can you please share what happened in your case finally?

the best way to compare if this iPhone is a fake is to look at the cams in light. if only one is deep deep blue or black and the other 2 are blue, then its fake. another way to check is by comparing the bottom bezel with another iPhone 13 or newer. if the bezel if thicker, then its fake. if it is fake, I am very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very sorry. apple won't do anything for u, but if you have an older iPhone maybe trade that in for money towards a new iPhone and put the fake one on eBay and confront the "friend" about this.

also a good value iPhone to get is the iPhone 13 brand new from apple, or if u like the colours, an iPhone 14. (the 14 and 13 have the same chip so ur paying $100 more for new colors)

sorry about this, and hope this helps :)🐶

It sounds like you have been scammed. When checking a genuinely new phone using the service page from @kb1951's answer, it should error out and say that the device is not yet activated.

If the iPhone is fake apple cannot do anything for you. They can only confirm or deny that it is a fake one.

I am sorry this happened to you

No. If you bought a counterfeit phone, Apple has nothing to do with it.

I whan to know if the phone is original or fake