How are the total cost of a Loan calculated?
I have this data and would like to know how I can calculate the total sum that I will have to pay to the bank:
13 Months, Loan Amount: 15132.08 Dollar
APRC: 12,0500 %
Interest Rate: 0,0795
12 Months: 528.83 Dollar
At the end bayback: 10233.17 Dollar
Service Fee: 35.00 Dollar Each Month
Here's an payment plan for this loan:
I would like to know how to calculate the total to pay sum
I would simply sum up the Service Fee and The Kredit amount (35 * 14) + 15132.08 but how do I calculate the complete Interest to come to 16786.01?
How would you calculate it? Thanks

The interest for each period should be the existing balance times the interest rate times the time. Your interest is just over $1\%$ per month, which should result in the kredit increasing by $1\%$ of the previous month's value. You can see it is not doing this, so they are using some other way of calculating the interest. The first month's interest should have been $15132.08 \cdot 0.1205/12 = 151.95$ The last month's interest (accepting their balance) should have been $10233.17 \cdot 0.1205/12 = 102.76$ Don't complain.