To create the surfaces at the front and back of the vehicle, you will need to follow the same procedure. You can then set tangency conditions to match up the surfaces. For the very corners of the car, create new surfaces using the two lines that are common to the adjacent surfaces and set tangencies.

Result of trying to simply use three curves to define front end (curves selected from left to right):

After redefining the nose surface by creating a curve at the bottom of the nose, splitting the curve at the front of the body the following result was obtained. Notice that additional datum curves were created on the body portion itself to aid in defining how the intermediate and rightmost curve should be defined at the intersection of the body and nose.

In sketcher, a centerline was drawn in overlaying the body curve (to determine slope) and the sketched nose curve was drawn to approximate the slope at this point. This is to get around the fact that it seems impossible to set C1 or C2 curvature at this intersection.

After adding a curve at the corner of the body and creating a surface to fill the gap (tangent to existing surfaces both sides):

The lower curve must be a separate datum curve that is tangent to existing curves used to define the front and sides (at the bottom of the car). In order to properly apply tangency conditions to the surface, the ends of the datum curve defining this surface must be tangent to the above mentioned curves. It may be necessary to do a use edge function on the existing curves and turn these into construction geometry to set the tangency.

After applying the same concepts to the rear of the car (making the surface at the center line normal to the sketch plane).