What's "manning" mean? Does it have to do something with "man?"

Is "yay" an exclamation? Should I ignore "yay" to understand this sentence?

"Yay" is an exclamation, however in this case "yay" is actually is just another way to spell the word "yea", which is an old way of saying "this". "Yay high" means "this high", and is used when people are describing how tall something is and know the approximate height but don't know the actual measurement, so they use "yay" or "yea" as a replacement for the measurement. It is also often accompanied by a hand gesture to show the approximate height of something as they remember it. Ex: The thief was yea high with blue eyes and dark brown hair.

Does "go a long way" mean "make a contribution"?

"Go a long way" is an idiomatic expression meaning to be very useful or helpful towards something. In this case, the speaker has used it to show that this research will be very useful or helpful in learning more about this iguana species. Ex: Your donation will go a long way towards helping cancer research. Ex: Getting a degree will go a long way in terms of career building.

What does "it" mean here?

"It" in the context of this sentence is referring to the keyhole that she mentions just before. The "keyhole" is a metaphor for having a limited amount of knowledge and ability, but then she says it is widened, which means that his amount of knowledge has the ability to become much greater.

When to say someone is “a natural”?

"You're a natural" means to be naturally good at something, or to be gifted at something. It must always be accompanied by the article "a" before "natural. Ex. She is a natural at tennis. You can also use "natural-born" when you want to describe a specific thing. Ex. You're a natural-born athlete. Ex. He's a natural-born artist.

What's "stick out" mean?

In the informal context, to "stick out" one's hand, arm, or any other body part or object means to reach out with that hand, arm, or object. Thus, "I stuck my hand out to protect him" means that he reached out his hand in front of him. Ex: I stuck my hand out to answer my teacher's question. Ex: The mischievous boy stuck out his foot to trip his friend.