Static mesh material change

Hi. I’m a little bit confused. Until now I’ve imported for example a door with its materials and with its textures. Because this is my first game, if I had 3 doors I’ve imported in each folder the same mesh with materials and textures. Now, I’ve created 1 material and I’m using it for all 3 doors but I’m confused with one thing.
When I change the material in Details Panel > Materials in my viewport the material is changing but when I enter inside the static mesh, there is still the old material + textures. And because of this the size of the door is doubled. Is this normal or it’s a bug or an error from my part? Next time should I import the new material inside the static mesh? Or on the materials panel ( outside )?
I’ve attached a pic where you can see that I’ve change the material but the preview of my static mesh keeps the old material.

I’m not sure what exactly you mean about the scale changing. Perhaps there is something funky going on with the import scale?

Think of the material that you applied in your Details panel on the right as an override for the object. If you dragged 1 of these doors into your world from your Content Browser, you would see that it has the default white material you have shown in your static mesh window on the left. If you were to then go into the “lambert4” material and change the color or add a texture, you would see this new door have the updated material.