As a phrasal verb, what does "jump in" mean? In what circumstances could I use it? Does it imply a negative nuance?

Please let me know how to use "since."

"Since" means from a certain point in the past until now; from then to now. You can use the word "since" when you are mentioning the past and how it affects the present. For example: Ever since I was a child, I have always loved ice cream. This sentence says that when I was a child, I loved ice cream and still love it to this day. Do not use "since" when talking about the future because it only applies from past to present, not to future.

What is “rose-colored glasses”? Is it really just red-colored glasses?

"Rose-colored glasses" is an idiom meaning you romanticize and only see the good qualities of another person, and ignore any bad qualities they have. Ex: The rose-colored glasses came off once I realized my girlfriend has bad manners.

What does “all hail” mean?

"All hail" is an old fashion way to express greeting or acclamation. It's not commonly used anymore and you won't normally use it when you're greeting somebody. Ex: All hail the Lord. Ex: All hail the King!

As a phrasal verb, what does "jump in" mean? In what circumstances could I use it? Does it imply a negative nuance?

To "jump in" means to suddenly become involved in an activity or situation, or to interrupt someone. You can use it when you enter a situation suddenly and with a lot of energy or you interrupt a conversation. Ex: May I jump into this conversation? Ex: Jim and I broke up. We jumped in too fast and got hurt.

What's the difference between the previous "racket" and this "racket"?

"Racket" in this sentence means to make a loud noise or commotion. The previous "racket" at the beginning of this video clip referred to the physical object of a racket used in the sport of tennis or badminton. Ex: Quiet down! You're making such a racket. Ex: Let's play tennis. I have tennis balls, do you have rackets?