Financial guru: Best retirement savings account for normal people?

At Finanzguru you can buy vouchers for almost all relevant brands (Rewe, Penny, Amazon, Lieferando, etc.) and get between 2% and 5% cashback in the form of points. These points (1 point = 1 cent) can then be automatically invested in the future retirement savings account offered by Finanzguru. You can store the cashback there until it is introduced and earn interest at 7%. Isn't that the best way to plan for retirement? Deposit a fixed amount every time