I sent money to someone and they scammed me

If you sent money using Apple Cash, then it is gone. Apple recommends to never send Apple Cash to someone you do not know. This is a cash transaction similar to giving money to someone on the street with the only recourse of asking them to give your money back. Here is how Apple explains it:

Apple Cash person-to-person payments are like any other private transaction between two people, so only send and receive money with people you know. 

Send and receive money with Apple Cash - Apple Support

Assuming that you used AppleCash and were not under physical duress, there’s little to be done.

Apple cash is treated just like CASH.

There’s no “purchase protection” whatsoever.

You CAN possibly report the fraud to appropriate law enforcement.