Review your first attached image. There is a box that is telling you information about the object that you have selected or highlighted. Within parentheses, it reads (locked). An object can be unlocked by going to the pull down menu "edit" then "locking" then "unlock". Then you'll be able to edit the item as indicated on your second attachment. The ability to lock an item, can be a powerful tool. Archicad has a world renown Help index - both textual and videos - try to go there as often as you can, to fully understand aspects and nuances of the software that may not be intuitive or readily obvious.
