Lend moeny to other person , with promisory note written

Hi Sir,

  I have lent some money to another person and I took promisory note for the same amount. dualy signed by the borrower  on 1/- stam paper and with 2 other witness

1)  Can this promisory note is a legal document?

2)  for how long is this document valid?

3) If the borrower is  troubling in repaying  the amount, how can I use this document legally to get my money back.

Can you please answer my questions.

Thank you,

Srinivas