The dashboard: I started from a box then extruded and sliced the faces, moved the vertices and finally I mesh smooth it.

 

The hole on the inner side of the doors:

The chairs:

After that I selected the inner faces (one by one) and extruded them inside and outside (-2,+2). Here is the result after mesh smooth:

The steering wheel: I created a tube and a cylinder , I attached the cylinder to the tube and then modified them with mesh edit then I mesh-mooth them:

The side windows, started from a box, modified according to the car-mesh them I mesh smooth them