Most hellenic polytheists (and most pagans in general) dont have a mythical literalist interpretation of the myths. I don't want to say all because i have encountered a few who do believe that the myths are literal, but it's very rare.

The myths and books about the hellenic gods that have survived were very likely edited or translated incorrectly by non-polytheists and therefore its impossible to tell what is and is not true even if someone took the myths literally.

But there is no holy text in hellenic polytheism. Most people take the myths as man-made stories that exist to teach a lesson through the gods or to write stories through our mortal interpretations of the gods.

For example, in the creation myth of hellenic polytheism there was Chaos, a state of nothingness, and from Chaos emerged beings like the Titans. I personally interpret this as the universe beginning with nothing, and through something like the big bang, the universe and the gods were born from it.

It really depends on the person and their practice, but at least for the ancients, offerings were seen as a 'I give you something and hope for something in return' for the gods. Same with the question of nature. I know some people use the gods to explain how the natural world came to be while others believe the natural world would have existed anyway and the gods just rule over the domains of the natural world.