Hi. First of all, let’s clean up your model.
Go to Monochrome Mode (View > Face Style > Monochrome)
You have reversed faces (blue ones) and not only that, but you also applied materials to those faces. Never apply materials to reversed faces. Always put them on the right side. I would suggest removing all materials and starting from scratch because it’s very messy. First of all Ctrl+A to select all geometry then click on this little icon to choose the Default Material Colour
Click on the geometry to get rid of your applied materials. Make sure you click on those reversed faces separately. Now that you’re rid of materials, let’s reverse your faces. Right click on one blue face > Reverse Faces and then Right click again > Orient Faces. This tells SketchUp to automatically reverse all blue faces of the geometry.
Now, about applying the same materials. It’s very easy. Ctrl+A to select all geometry > pick a texture > click on any face and voila!
Tip 1: Don’t forget to get rid of materials you don’t intend to use
Tip 2: If you’re not familiar with this, look what Aaron has to say about how important Grouping is: SketchUp Skill Builder: Groups vs Components