What Is the Best Way to Pay Off an Equity Loan?

loan

I have taken an justice loan for 300 months with an interest rate of 8.24% and making a monthly payment of $197.07. Along with making the monthly payment I am also wanting to pay this off as early as possible by paying $400-500 monthly on the principal. How can I calculate how long this will take to pay off by paying this amount on the principal and is it surpass to pay on the principal weekly, bi-weekly or monthly. Thank you in advance for your responses!