The benefit of paying extra on a mortgage isn’t just in reducing the monthly interest expense a tiny bit at a time. It comes from paying down your outstanding loan balance with additional mortgage payments, which slashes the total interest you’ll owe over the life of the loan.
By paying N$50 extra on a N$500 000 Home Loan with a 10% interest rate for 20 years, you will be able to pay off your home loan in 19 years and three months, while saving over N$24,941 in interest that you would have paid to the bank.
You should also consider paying a lump sum if you get a bonus at work for example.