I know

Say this when there's something that's annoying or difficult for other people, but you can't fix it.

I know; you don't want to be here. But there's nothing we can do about it, so we might as well enjoy it.

not exactly (something)

This is an example of understatement. If you're talking about someone and say:

She's not exactly poor.

...it means that she actually has a lot of money. Instead of simply saying "She's rich", you might use this expression in order to sound witty and intelligent.

Here's another example: if your husband is overweight, but made fun of you for being a little heavy, you can say:

You're not exactly in the best shape yourself, you know.

"Not exactly" can be followed either by an adjective, or by a noun:

A: You're dumb.

B: You're not exactly a rocket scientist yourself.

(something) rolls off the tongue

When a name or word is easy to pronounce, we say that it "rolls off the tongue". You can use it in a positive sense like this:

His last name is Lane, huh? So you would be Lisa Lane? I like it; it kind of rolls off the tongue.

You can also use it in a negative sentence like the example at top.