Atheism doesn't propose such a thing. It's just the philosophical standpoint that denies the existence of deities. That's all. Topics such as afterlife, souls and other metaphysical stuff is outside of its scope. There are schools of Buddhism that deny the existence of god but believe in reincarnations.

Atheism isn't a believe system. Same as "not stamp collecting" isn't hobby. Not believing in god doesn't mean a person can't believe in other supernatural stuff (UFOs, chakras, whatever).

BTW, the view that you describe about reality not existing outside of your own mind is called solipsism. That position stands on epistemological shaky grounds though.