I've been learning lately about Buddhism and I have several questions about it. I haven't actually read any of the sacred books, just some stuff on the internet and now I'm reading What Makes You Not a Buddhist as an intro to Buddhism, so I might have some misconceptions about it.
So let's get to the questions:
1) In What Makes You Not a Buddhist the author says that asking a Buddhist about the meaning of life is inappropriate because it implies that somewhere there's a final purpose of being. Do Buddhists believe that there's no purpose in living? And if there is, what is it based upon. Where is the motivation to do anything if it isn't building up to something? Why be good/smart/compassionate/... ? And why not commit a suicide instead of learning and understanding things so that you don't suffer - wouldn't that be faster?
2) If I understand correctly Buddhism says that we don't exist, we're just made up of different parts and our conception of ourselves is just an illusion. But if Descartes was right when he said "I think, therefore I am.", then I don't see how that works with Buddhism - someone here must be wrong (I think). Do Buddhists believe that there's no essence that is "me" (like soul in Christianity), just random parts connected together in a certain point of time? If yes, then what is that thing that thought of the illusion of existing(Is it our mind? Does it also not exist?)?
3) One of the four seals is: All compounded things are impermanent. In the book author says that all things are compounded so saying "All things are impermanent" is equivalent. How is that even possible if anything we understand about the world is true? Everything is made out of atoms and atoms are made out of subatomic particles and perhaps those are made out of sub subatomic particles and so on (I don't know), but in the end, there must be a basic building block that makes those things and that's bound to be constant. It's hard for me to understand how everything could be a compounded because that means that it's made out of smaller things put together. But if those things are also compounded, this process goes on infinitely. But there's no infinity in nature.
I'll really appreciate the answers.
EDIT: Thank you all for the great answers. They really helped me understand some things better. Because I hate deciding on which answer is the best, I'll let the community do it - after some time I'll pick the one with most upvotes.