(something) is cool

There are several meanings of "cool". Of course, there is the original meaning of "not hot". But other meanings include:

• popular
• interesting
• relaxed and not easily stressed

"Cool" started off as slang, but has been used for so long that it's OK to use in most situations. A normal adult can use the word "cool" in any of these situations:

• talking to a friend or family member
• in a business meeting
• talking to someone they just met
• in an email message
• in an advertisement

Situations in which it would be (just a little) strange to use "cool" are:

• if you were born before 1940
• in a written essay

everyone there seemed (adjective)

This is a good way to describe a group of people you met at a place or event. 

A: How was the party?

B: It was okay… everyone there seemed kind of cliquey.

 ("Cliquey" means that people only stick to their own social groups.)

I stopped going to the Red Room because, like, everyone there seems so young now.

super (adjective)

“Super” is very popular, especially among younger English speakers. You can use it before any adjective to make your meaning stronger.

It’s a super long movie, you know.

I was super tired after so I just stayed home.

You don't need to worry; she's super nice.