dimensions, built in corner desk, stair landing, etc.

[fortune5mom]

I;'m a rookie with the software and with asking for help, so please be patient. A few trouble spots: 1) I want interior dimensions to show from inside wall to inside wall for furniture placement etc.- I can only seem to do that when 2 interior walls are used, rather than an exterior & interior (this shows inside of interior wall to outside of exterior wall).

2) trying to add a desk in corner where 2 base cabinets on perpendicular walls support a granite slab at a 45 degree angle to the corner. How can I do this?

3) I have a 2 section staircase (up and back, rather than up and left or right). At the top of the first flight (7 treads), there is a 39" square landing, a right turn, and up one step onto a second square landing, then right turn and 6 tradfs up to second floor. How can I make the landing split so that there is one rise in the middle of the 78"x39" landing, making a total of 14 steps up?

This shoudl keep me going for a while, but I'm sure more to come. Thanks in advance.