What does "hide out" mean?

What's "pandamic"? In what situation is this word used?

A "pandemic" is a disease that is widespread throughout a country or the world. You can use the word "pandemic" after stating the name of a disease that would be considered a pandemic i.e. it is widely spread. Ex: The coronavirus pandemic has changed the way people live.

In English, it seems there's a lot of figurative speech about the tree. Why is that?

In mythologies, legends, and novels, trees represent "growth" and "life." Trees are easily referenced for symbolism and meaning. It also centers on a lot of religions like Christianity, where one of the first bible stories is about the tree in the garden of Eden. I don't think there's one specific reason as to why trees are used a lot figuratively, but rather that trees are a part of nature, and thus part of the human experience. So inspiration is taken by nature and living things that humans live in and around!

Is "take it now or leave it" an idiom? What does it mean?

The phrase "take it now or leave it", is not technically an idiom. However it is very similar to the idiom "take it or leave it", which is said to express that an offer someone has made is not negotiable and that the person is indifferent to another's reaction to it. In this song I believe they are simply changing up the idiom "take it or leave it" and that is what they mean. Ex: That's my offer, take it or leave it. Ex: Look, you can take it or leave it.

Is it okay to not put "a" in front of "great opportunity"?

No, it does not make sense to remove the indefinite article "a" here from this sentence. Articles are used to modify nouns. In this case, the adjective "great" modifies the noun "opportunity". However, articles must still always be used before adjectives which modify nouns. Ex: She is a sweet dog. Ex: It was a long day.

What's "franchise" mean here? I know MacDonald is a franchise, but I don't know what that means.

Here, "franchise" is a title or concept turned into a series, such as a television show or movies, and is used to market different products. Ex: I love Marvel's franchise! I've watched all the movies, read all the comic books, and even have a mug with Iron Man on it. Ex: Harry Potter is a successful franchise. Kids still watch it these days.