Can someone help me analyse my VERY HIGH INTEREST LOAN?

So long story short, my credit isn't so good. I had an emergency and needed a vehicle. Well I got this car with a HIGH interest rate of 28%. I'm trying to pay this loan down soon. The terms are 72 pymnts of 202.00. (payments are due on the 2nd and 17th of everymonth, semimonthly pymnts). So my plan is to pay extra with each payment to pay it down. I can afford 400$ in total with each payment. In how long will I pay my loan doing that? I would gladly appreciate your help!!!