Split levels in Sims 4??

I’m trying to make my grandmas house in Sims 4 on Mac but after some light research noticed it is not possible to join rooms at different levels. I’m trying to do a raised back split - is this possible with the current tools? 

Here’s what i need all connected… 

- main floor on a 4 block tall platform from terrain height

- back half of building is lowered 50% in the terrain 50% out, ceiling of “lower level” should be halfway up the wall height on main floor 

- 2nd floor on back half stacked over lower level, also lowered relative to lower level height, and again the floor height of the upset level should be halfway down the height on the main floor

Look at attached images - this is the best i could create however it is not functional and i can’t put things like a door on the main floor. 

To get this: 
Essentially i made the lower level and main floor at the same time on the same depth just below terrain level, and drew walls to split them up as 2 separate rooms. I left the lower level portion sunken below terrain level, and raised the main level platform all the way so the walls are only like 1-2 blocks tall. Then i made second floor stacked directly above the “lower level” AND main floor. I then again drew the walls to split to “upper level” and main floor room shapes . Lastly i deleted the floor on the 2nd level at the main floor shape - This way it looks like the main floor has taller walls (which isn’t needed). Finally added stairs where required.

If anyone has ideas on how to go about this differently or me knows any ways around this please let me know, thanks!!