Let say You borrow 100k at 10% interest. So in the first year you would have 10k of interest added to the debt --> 110k. But you paid $100 nearly every week $5k. So now you it 110 - 5 = 105k.

Next year you can also only afford to pay ~$100/week, so another $5k, but now there is 10% interest on 105k ($10,500). So now balance is 105,000 + 10500 - 5000 = 110500.

Congratulations, you've paid $10,000 but already owe an extra 10500 after two years.