On billiger-mietwagen.de you can request child car seats under the item "Extras" during the booking process. You will find the relevant field in the "Driver & payment method" step.
We will then contact your rental company and reserve the child car seat for your rental car. In the booking confirmation we list the costs for the child car seat so that you get an overview of the total price. You will have to pay for the child car seat on site. If you decide at short notice to take your own child car seat on the trip or if you do not like the child car seat on site, you can cancel the reservation without being charged for the child car seat.