Answers to 3 and 4 are related. I mean, we're born to do something here whether great or small things. If you are a godly person, you might say your god wants you to do the best that you can and live life to the fullest ( yeah, sounds geeky ). In general, you should find things that interest you and just do it ( no matter what people say). This will keep you from killing yourself. After death, well, actually no one knows what happens to us. Wether it's the end of it all or another life is waiting for us no one alive really knows.
So, enjoy your life cause you will not know when it will end.
And for number 1, Again, no one really knows where we come from (if you are asking the spiritual or biological aspect of life). Even as of this moment scientists and religious leaders are still arguing about the evolution theory and lots of things that will spin your head. It's like asking yourself which came first the chicken or the egg.
This brings us back to, you guessed it, ENJOY your life.
