Welcome! To upload a file (a SketchUp model .SKP file, or an image, or whatever), use the seventh button from the left when composing a message - it looks like an inbox tray with an up-pointing arrow. I’m not sure what are the restrictions on uploading for a very new forum member. A general restriction is a limit on file size of 3MB maximum.
Regarding the modeling issues you are facing, I noted you are using layers. Be very careful when using SketchUp’s layers. They do not behave the way 99% of new SketchUp users expect them to behave. A SketchUp layer is simply a tag for visibility of the items associated with the “layer”. In particular, the use of layers has no effect on whether raw geometry bits and pieces - edges and faces - merge and interact with each other. In other words, two rectangles that are associated with two different layers will happily merge and mush into each other, if they touch in 3D space.
So, some advice:
- Be sure that all raw geometry - edges and faces - are always associated with “Layer 0”.
- Keep “Layer 0” the active layer at all times (which goes a long way to ensuring point 1).
- When you have identified a set of geometry that represents some more-or-less independent “thing,” create a Group or Component to hold the thing’s raw geometry. This could be a wall, or a set of adjacent walls. Groups and components can be nested, so you can have a North Wall object, a South Wall object, etc. and then collect the various walls into a First Floor object.
- If you want to control visibility of objects via SketchUp’s layer feature, associate those groups or components with various layers. Do NOT associate any of their actual edges and faces with a custom layer; only associate the overall group or component with the custom layer.