why is our generation so materialist?
That one is easy. Because you/we have been raised that way.
The other two questions you ask are not so simple to answer. An answer that might satisfy one person may be entirely unacceptable to another. I do know one thing though, from experience.
I was a lot like what you describe when I was 15. I'm 32 now, and I am on my way to discovering my own answers. But what do these answers do? Why do we need to know?
There is, as far as I can tell, only one issue that is truly important, and that is happiness. Which answers do you need in order to be happy? And I don't mean happy as in deliberately ignoring everything that makes you miserable. I mean, how can you live your life, accept your responsibilities and maintain a positive outlook through it all? Tailor your questions to that end and you may save yourself a lot of problems.
As for why we are here and what the purpose of this life is, I have my own answer to it: Find out what you love doing. What comes as naturally to you as breathing? That's what you are meant to do. If you don't know what it is already, figure out what it is, and then work on how you can do it for a living.