mid-western (girl)

I'm mostly a mid-western girl; I've lived all over the mid-west.

The 'mid-western' states of the United States include Illinois, Iowa, Wisconsin, Minnesota, Michigan and North  and South Dakota.  It is the middle region of the U.S.  A 'mid-western girl' would come from or live in this part of the country. Notice the following:

1. Mid-western people have a reputation for being nice.
   
2. They serve very mid-western food here.
   

grew up mostly

I grew up mostly in Michigan.

If you 'grow up mostly' in one place it means that you lived there almost all of the time when you were growing up. Notice the following:

1. He grew up mostly in the northwest, in places like Seattle.
   
2. She grew up mostly at her grandparents' house.
   

doing their own thing

Everyone in Chicago is always busy, and they're doing their own thing.

When people 'do their own thing' they have their own personal plan or things that they like to do.  It means that people are independent.  Notice the following:

1. I think I'm going to do my own thing tomorrow. I need some time alone.
   
2. My kids are teenagers and are really into doing their own thing right now.
   

exciting atmosphere

It's fun to be in such an exciting atmosphere.

When we are surrounded by places and people that are fun and interesting we are in an 'exciting atmosphere.' Notice the following:

1. It's a very exciting atmosphere to walk around in.
   
2. She likes working in an exciting atmosphere, like a restaurant or bar.
   

good food

Does Chicago have a lot of good food, a lot of good restaurants?

'Good food' is food that is delicious or tastes good. Notice the following:

1. They only make a few different things here, but it's good food.
   
2. We go to the festivals for the good food.