Your faces are inverted.
Open the file, and in Edit mode click the ‘Show Overlays’ button on the top right section of the tool bar.
Click on the ‘Face Orientation’ button and it’ll show you blue faces for outward pointing faces and orange for inward pointing faces.
Select all (press A) then go to your Meshes tool drop down and select ‘Normals’ then select ‘Recalculate Outside’ to flip the Normals of the Faces.
Actually I had another look at your model. You’ve got extra faces inside the ‘teeth’ of the main parts of the doors that don’t need to be there. They will affect shading on the outside faces of the door because Blender is calculating a squared edge from the inside of what should just be a flat face.
The edge meshes of the teeth also have extra faces on the inside edges of the teeth. I’m guessing you want them a different colour than the doors, but if you can get rid of all the Faces that don’t show then you’ll save the graphics rendering a little bit of work trying to draw them.
In the future when you get into more curved shapes:
Select All
Mesh Tools
Normals
Reset Vectors
This’ll help smooth out the strange edge shading that happens when the Normals of curved edges and Faces get a little twisted.
There are also many many tutorials about using Blender that helped me out a lot when I was learning how to create meshes.