how long dous it take????
Many years, plus lots of traveling to get to know all the cars brands in other countries
No one can... You can learn your forte and that's about it. I've yet to find someone who knows every car exported to their country in the past 20 yrs, let alone every car in general. You have to remember for every major car company that you've heard of, there are many small companies you've never heard of... The refrigerator company that originally made the Isettas for example... I'd be willing to bet 90% of the people on this site don't know that companies name without looking it up. And how many people know of the Schwimwagen (spelling likely isn't right there) So your answer is a lifetime and you'll still fall short.