Hello, I hope the following assists you.
The rear seats do come out on a Cmax, to start with fold the seat back down until it locks. You can then see a handle at the back of the base, pull this to flip the seat up, when the seat is at approximately 45 degrees you should see some red levers, move these to release the seat, you may need to wiggle the seat a little to release, it is a kind of hook retaining mechanism. Be careful when you lift the seat as they are quite heavy.
Below are a couple of images that show the release mechanisms for the seat.
Attachments are only available to registered users.
You can see the release lever on the rear of the seat above, the seat is folded and released in this image.
You can see the red release lever above.
I hope this helps but if I can assist further let me know and I'll reply as soon as I'm able to.