I borrowed money from a private person and paid it back. As a result, he used my signature to borrow money. He can take the following steps:

1. Collect evidence: collect all relevant evidence, including loan agreement, bank records, loan documents and other possible supporting documents.

2. Contact the parties: communicate with the lender to show dissatisfaction and disapproval of the loan behavior. Ask them to provide relevant evidence and documents, and ask to solve this problem.

3. Seek legal aid: If the problem cannot be solved through communication, you need to consult a lawyer and seek legal aid. Lawyers will provide appropriate legal advice based on the evidence and circumstances provided, and help to take further legal actions.

4. Handling of reporting: If fraud or illegal acts are found, you can report the case to the local police and provide relevant evidence and detailed explanations. The police will start the corresponding investigation procedure.