Yeah. It seems that I was too sloppy when calculating APR %)

The numbers you gave look self-contradictory to me, but assuming that your APR is around 6% and loan amount is 160400, in the first year you have 160400*0.06= 9,624 of interest. Divide it by 12 month and we have €802 in interest in a month. As you can see, vast majority of your €900 payment goes to interest and almost nothing to repay your loan in the first year. That's why it takes 38 years to repay it. As you payed back almost nothing in the first year, the situation would be almost the same in the next year. In theory you can have interest equal to your payment, your loan will be perpetual and you'll pay infinitely more for interest than loan itself.

If you want to pay less for interest, you need to shorten the term of the loan by either borrowing less, or by repaying more.

Disclosure: my calculations are "back of an envelope" and sloppy and probably not exactly how your bank calculates the interest. It's for demonstration purpose only.

Edit: typos.

If they can. OP should look if his mortgage contact allows early repayment toward principal, and what the terms and procedures are.

In geology, mineral must also have crystalline structure. So, obsidian is a natural inorganic rock, but not a mineral, because it's a glass, not a crystal or a bunch of crystals.