Attic wall issues . .

[Tundara Homes]

I have a plan with multiple ceiling heights running along an exterior wall. I am not sure if I am modelling this correctly, but I can't seem to clean up my attic walls. I have been told that if you break walls here and break walls there, it should work. My usual work around is to add a siding layer with polylines but I would like to learn otherwise. Please teach me what I am doing wrong . . .

Thanks for your time.