Just curious, but does the word "celebrate" and "celebrity" are somewhat related? They sound so similar!

What does "sinker" mean?

A hook, a line, and a sinker are all different components of a fishing rod used to catch fish. Sinkers are small weights attached at or near the end of the line that help keep the line under the water. Ex: My grandma fell for an insurance scam hook, line, and sinker. Ex: I lied to my boss that I'm sick, and he told me not to come to work this week. Hook, line, and sinker.

Why is it "I'm focused on", not "I focused on"? Or can I say "I'm focusing on" instead?

You're right in that the two phrases are similar. However, there is a subtle difference to them. "I am focused" has more emphasis, it implies that all of your attention is on this one thing. It also implies that it is an ongoing action. "I focused on" is used more loosely for things that don't have all your attention but you still think is important. It can also mean a past thing that had all your attention, depending on the tense used. "I am focusing on" would be used for something that you are currently focused on. So in the case of this video, you absolutely could replace "I'm focused on" with, "I'm focusing on". Ex: I focused on my homework. Ex: I'm focused on my homework. Ex: I'm focusing on my homework.

What is the meaning of "dilated"?

"Dilated" in this video means to be enlarge, to make wider or more open. You may already know this, but when a woman has a baby, her cervix needs to be dilated at least 10 centimetres before she can start pushing. In this video, Rachel is upset that four other women are having their babies before her and is saying that she is dilated only three centimetres, not enough for her to start pushing. Ex: Her eyes were extremely dilated. Ex: His wife was dilated at six centimetres; not enough to start pushing. Ex: The medication is going to dilate your pupils in your eyes.

Is there any words that can be used instead of "particular"?

Here particular is being used as an adjective referring to a specific thing rather than others. Therefore some good synonyms in this particular context would be "special", "specific" or "certain".

What does he mean by saying "I just got that"?

Informally, "to get something" means to "understand" or "realize" something. So, the speaker is saying "I just got that" to mean that he only just understood. He likely has a somewhat slow personality, so he had a belated understanding of the situation. Ex: A: Did you get that? B: Yes, I think I understand what you're trying to say. Ex: I didn't get what she meant until long after the conversation had ended.