Listen, this reminds me on my first attempt in Chief after 20 years with AutoCAD.
Don't take me wrong, but this is a mess. After I did many similar stuff in the beginning, let me give you a friendly advice - don't try to fix this plan, it's less work to start all over again.
But first you must get familiar with how this software works, and with basic concepts.
I will not start with endless count of mistakes, but ... you just have to start over.
Chief works really good, if you spend some time on settings first, and do that part wright. Pay special attention to Wall Structure Settings - when you really understand that part, it will go much easier.
David Michael's site chieftutor.com is excellent point to start, also, dshall's YouTube channel, but after you go through first one.
Also, official Chief Architect support video's are good learning source, but if you go from start and not skip any...
Maybe you should start with watching Dan Baumann's https://www.youtube.com/watch?v=AuIPzVulvG8, watch entrie set of videos, and then start all over. These 7-8 short video's will give you a perfect overview and ideas how to start.
When you start all over again, just do it like you are on construction site, and just use logic - how will you really build it in a real world.
Most important is to set your ceiling heights for entire floor, and not to mess with it - when you finish all floors, if you need to change something, first look how to do it on YouTube - Google for platforms and split level.
-This cross section is a real headache. I just can't figure out what you did.
Also, it would be a good idea to align the walls, and close them properly.
This stairway problem is not really clear - is that a mistake, or stairwell makes this strange corner at left angle...
Good luck , and keep in mind that Chief cannot read yours.
