You have to prepare for the public retirement system (and also the small state pension system) to be insufficient. The system is currently designed to fall short intentionally! Most sources recommend to save 15-20% of your net income for your retirement. If you really want to be safe, I highly recommend that you calculate your actual pension gap (that is the total sum of money that you will need to spend the rest of your life after retirement to keep your current quality of life). Once you know the total amount of money you need, you can then calculate what your current pensions sum up to. The difference it the gap that you need to save. When you know how much you need to safe totally, you can calculate what savings rate you actually need at minimum to keep your lifestyle.