Okay, so I attempted 2 methods for designing a BMW M3 2004 model but I fail at the end. By fail, I mean I can’t continue since there are too many vertices to move around. I was thinking of starting off with a simple car. Any simple car suggestions. Also, how would one design this car. Box method or detailed method. I tried both of these for the BMW but always hitting a dead end. You may say “Try something easier instead of a car” but dammit, I want to model a car. How does one know if their ready to model a car?? 
There are a lot of tutorials out there on car modeling. Rob Tuytel has made one on youtube which is very good.
Also if you really want to get into it, you might want to get yourself the car modeling course made by cg masters. Check their website out for more information.
You might not get the perfect result straight away. But with time and effort !