How to know if its safe to ship this item? (Payment Through Paypal)?

So i'm trying to sell my iphone 6 and today someone contacted me and offered me 700 dollars including shipping costs (i wanted 510 dollars for the phone) The shipping address is in Nigeria and the shipping costs are going to be quite high (50-60$) I have received an email from paypal saying i have received 550$ of the money and the rest will be there once i send them proof of delivery. This is my first time using paypal and i'm afraid of fraud. Can someone provide me with any guidance?

That is a total fraud - paypal is a bank and has nothing to do with the buyer/seller relationship.

The email supposedly from paypal is a fake.

If any money appears in your paypal account, it will likely be from a stolen credit card and get taken back after a few days.

Have nothing at all to do with the supposed buyer. If they make any threats, contact the police.