Sadly you were scammed by fake, spoof paypal emails.
Paypal NEVER tell you to send an item before the payment is showing in your paypal account. Paypal do not tell you to send trackable, they advise it for selling protection but it is not compulsory. Paypal NEVER expect you as a seller to send money to receive money !!
Advice is VOLUNTARILY given. Please leave Kudos / Solution if I have helped you.