A lot of these ancient texts have stories embellished around some actual events that may have taken place.
Some of these stories are metaphors and some of these may have been misinterpreted.
For example, Ravana had the intelligence of 10 men so it was like he had 10 heads has been interpreted that he literally had 10 heads.
No I do believe the Guru Nanak squeezed blood out of bread, but my point was if you need scientific validation for faith, e.g the yugs can't be real because it goes against science, then in that case much of Sikhi is false including God.
So you can't really say oh I believe In God but I don't believe in the yugs because theres no proof for that, because there really isn't proof for any of it tbh.
That's why it never makes sense when people try to make their religion sound more valid by comparing it to science, because faith and science are two completely different things.
As for Ramayan, well Ravaan is mentioned in Guru Granth Sahib ji aswell, so is shishnaag a cobra with a million heads.