end up (doing something)

This phrase is used for telling the final result of something. It can be used when telling stories, like in the example above. It can also be used for predicting the future consequences of an action:

If you keep missing classes, you're going to end up failing your grade and having to repeat it.

Another phrase that's similar to "end up" but more casual is "wind up":

After we left the bar, I wound up going over to James's place and sleeping on the couch.

stick around

"Stick around" means to stay. It is a more casual way to describe staying somewhere. You can use it when talking to people in social situations:

Hey, why don't you stick around and have dinner with us?

I'd love to stick around, but I have to go pick up the kids from soccer practice.

Or you can use it in professional situations if you want to sound casual:

Hey, would you mind sticking around for a bit after the meeting? There's something I want to run by you.

the work day

Your "work day" is the hours when you start and finish work each day. You can talk about your work day like this:

My work day is from 8 a.m. to 4 p.m.

(telling time)

Here are some of the ways of saying what time it is.

For the time 4:00:

Four

Four o'clock

For the time 4:15:

Four fifteeen

A quarter after four

A quarter past four

For the time 4:30:

Four thirty

For the time 4:45:

Four forty-five

A quarter to five

For the time 4:05:

Four oh five

Five after four

the official (something)

Something that is "official" is approved by the authorities (the people who are in charge). "Official" things are often written down or recorded somewhere.

When is the official start date?

They tell me that I've got the job, but I don't know. They haven't sent me an official offer letter or anything.

We often compare the "official" version of something to how it actually is in reality:

My official title is "Executive Coordinator" but basically I'm a secretary.