A car that has been repossed by the company that signed out the loan they can take it resell it and add interest to whats left of the loan when their not suppose to they want as much money as they can get their hands on it isn't fair business what they do

If your car is repossessed due to non-payment or late payments, the bank or loan holder can resale the car. Often, they will sale the car through an auction. People who attend, of course, want to pay the least amount possible. So, the loan holder, takes the highest bid, which is often substantially less than the amount owed on the car. Legally, the loan holder or bank can ask you to reimburse them for the difference of what's owed and what they received through the car sale. They can continue with whatever amount of interest you agreed to when you signed for the loan. You can attempt to compromise with the loan company for lower amount owed on the car or consider filing bankruptcy as a last resort.

Yes, it is normally. It's most likely in the agreement that you signed at the time of buying the car.

Of course the interest will continue to accrue. Interest is a charge to the borrower for loaning the money. This is how the banks make money. Whether or not the the car was sold, if there is money still remaining to be paid, the interest will continue to accrue until the loan is paid off.

It sounds like you have not really been making payments on the loan. If you had a balance of 18K, and it is currently at 19K, you have not been making timely payments.

You should contact the creditor to see if you can work out a negotiation or a settlement.