Help please... basic problem... all my walls are deleting

Hi all, I’m very new to Sketchup and I’m finding it quite hard to navigate (currently studying). I’m using the study resources I’ve been provided, but I keep running into small issues and I’m not sure how to troubleshoot fix them. My attached floor plan has two storeys, the first floor, I had forgot to add a wall so have now added it in. When I go to remove the line from the rectangle, I used to add the wall in, it deletes all my walls. I’ve tried a few different things to correct this, but I’m getting stuck. I also tried to add in a door opening using a rectangle and then delete the lines, but it also deletes all the walls. I know this is such a basic fix / basic error I’ve made somewhere, I’m just struggling to fix it. I would be so grateful if anyone could please help!
Thank you

It would help if you’d share the .skp file so we can see exactly what you have set up. One important thing that you need to keep in mind is that ALL edges and faces should be created and remain untagged. Only groups and components should be given tags. When you start tagging geometry (edges and faces) you can create all sorts of problems for yourself.

Thanks Dave. This is the file. Sounds like I might need to remove my tags and groups to remove the lines then retag and regroup maybe?
Module 4 Floorplan 2024 #5.skp (116.4 KB)

You need to go through the model and create groups or components for the discrete objects in the model. Then give the tags to the objects, not the geometry. I fixed the incorrect tag usage in your model.

If the instructional materials you’re following don’t teach this, I would suggest finding different materials to follow. Maybe start with learn.sketchup.com

Here’s the file.
Module 4 Floorplan 2024 #5 dr.skp (17.3 KB)