What does he mean by "I'm down" and "I'm out"?

What's "fall into" mean?

To "fall into" something means to come or go down by the force of gravity into something. To enter into something by falling. Ex: I fell off my bike and into the bushes. Ex: Don't fall into the river!

Is it common to use "trick" as a meaning of "know-how"? Could you give some examples?

Yes, it is common to use the word "trick" to refer to a skill that someone does that helps them achieve a result or succeed in doing something quicker or better. A "trick" in this case is something that someone knows how to do that is often a short-cut of a longer way of doing something. Here's a few examples: Ex: How do you whistle? What's the trick? Ex: What's the trick to writing a good resume? Ex: The trick to making strong coffee is to use less water.

Could you tell me the difference between "hate" and "loathe"?

"Hate" and "loathe" are similar in meaning, but the connotations of these words are different. The word "loathe" is a stronger word than "hate." If you loathe something, you absolutely hate it and can't stand to be around it. The word "hate" is a strong word for dislike, but not as strong as the word "loathe." Ex: She hates me. Ex: I absolutely loathe the snow. Ex: We hate fast food restaurants. Ex: He loathes public transportation.

What's the main difference between a multiverse and a parallel universe?

Good question! A "parallel" universe would be a copy of a universe one like ours that exists alongside ours but is undetectable. Whereas "multiverse" means that there could be many universes around us that we just don't know of. The main difference is that multiverses may not match our universe, but a parallel universe would be very similar. Ex: In a parallel universe, I'm probably a doctor instead of an artist. Ex: I hope one day we discover multiverses.

Why did she say "certificate", not "baby"?

"Certificate" here is referring to a "birth certificate". A birth certificate is a document issued that records the birth of a child for vital statistics, tax, military, and census purposes. In the United States, birth certificates serve as proof of an individual’s age, citizenship status, and identity. They are necessary to obtain a social security number, apply for a passport, enroll in schools, get a driver’s license, gain employment, or apply for other benefits. So she is asking them what name they wish to put for the baby on his birth certificate.