To start modelling a front part of the car, you should hide lots of vertices on rear part, side and almost all vertices in front area of the shape you've modelled earlier. All these vertices are unneeded currently. Also, since you know how and where Create\Polygon\Strip tool will place vertices, move Pivot helper somewhere into an area shown pink on the right image.
The second thing to note is that we shall model only half of the car body. The mesh is symmetrical, so half of it can be copied and mirrored later. It's just like you don't need to model all four wheels - you create only one and clone it. So, keep in mind that vertices should not go out from the light blue area. Moreover, vertices should end exactly on solid blue line so there will be no gaps between two mirrored halfs of the mesh. Been an advanced modeller, I've created headlight with quads initially. Pulled the vertices to their positions and find the mesh quite clean and accurate now.
Now, frontal air intakes are on a run. I insist that you model them and not avoid this detail. Pair of these intakes is a key of all BMW models. You can omit whatever else, but these air intakes is what make the model recognizeable with even a quick look. I've modelled the one and selected polygons. Image on the right is an example.
Once air intake polygons selected, pick a Modify\Submesh\Extrude tool,
switch to selected and Screen-Z mode. Make sure Move
interaction mode is set in Extrude tool options; "Shap edges" is Off and "Quad
sides" is selected. Then click and drag in front view - to push air intake
polygons into car.
Now you can create a front bumper. We don't have top blueprint, but you can
still use top view to shape an accurate curve of the bumper. Extrude tool
can be used to pull a license plate out from the bumper, and/or you can use
this tool to push a row of polygons in the bottom of front bumper. I've rushed
into details a little and result might be messy somehow. In certain cases
blueprints might be not enough to model certain details and curves, and you
can refer some photos to examine how you should lay polygons properly. Top view
have only be used to shape curves on the hood. In general, there should be now
zig-zag lines on the mesh - most of lines form intersective curves and that is
what you should be aimed to.
Modelling Rear and Top.
There are no that much things to explain how rear and top were modelled. The
only thing to note here is that top and windscreen were modelled in top view
(without blueprint). Everything else is exactly as the rest of mesh was
modelled - no extra tools were used.
The result of this lesson is in Files\les3_05.z3d file.