You're right, we do not know. Through personal experience, I believe that I know that we all have souls that don't die but that can't be proven, any more than a follower of any religion can prove their 'God' exists or that reincarnation is a true thing (I think/believe it is). But who can say that I'm right and another person's beliefs are wrong? I suppose we'll only know for certain when we die.

If the universe is eternal then, by definition, it wasn't created and thus it won't die but if Hinduism is right then this is merely one universe in and unending chain of universes which means our universe is not eternal and will 'die', but the 'chain' of universes is eternal, whatever eternal means. It's a word whose meaning can't be grasped by the human mind.

In the meantime, I'll continue to try to live the best, most giving life that I can. And I sincerely hope that I'm right and there is no eternal punishment waiting for me on the other side.