How listing

How display a child pages when I am on parent page?
Here everything is ok http://rawlplug.de/produkte/
But when I am in http://rawlplug.de/produkte/chemische-befestigungen/r-cas-v/ the left menu disappear.

Second question:
How display on child page all featured images?
For example here: http://rawlplug.de/produkte/chemische-befestigungen/ I would display featured images from this 6 pages on left.