how to get my money back on apple pay that i sent to wrong person

Apple recommends to only send money to people you know since this is a private transaction between 2 people. Since you should know the person, the resolution is to ask them to send the money back. If they have not already received the money, you can cancel the transaction. Apple Cash does not offer the protections like a credit card and is just like giving someone on the street $20. This is detailed here:

Send and receive money with Apple Cash - Apple Support

If you don't see Cancel Payment, the person has already accepted the payment. Try asking the recipient to send the money back to you instead.

Depending on your bank or card issuer, it might take 1-5 business days for the money to be refunded. 

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. If you have questions or concerns about a transaction, please contact us.

You may not be able to, depending on the time frame involved.

Apple Cash is a service that’s administered by Green Dot Bank. Contact an Apple Cash Specialist at Green Dot Bank by calling (877)-233-8552 or by calling 1-800-MY-APPLE

https://applecash.greendot.com/termsconditions/