that kind of behavior

A person's "behavior" is the way that they act. You can have "good behavior" or "bad behavior". But the phrase "that kind of behavior" always refers to someone who's doing bad things:

I do not engage in that kind of behavior. Unfortunately, that kind of behavior is common in large companies.

(something) would be (adjective)

Say that something "would be ___" to describe an imaginary situation. In the example above, the speaker is imagining what it would be like if the cashier acted that way in her home country.

(something) is totally unacceptable

Use this phrase to talk about things that someone must not or should not do. Parents, teachers, managers, and other people with authority use "totally unacceptable" when they're yelling at someone that they're in charge of. Customers also use it to complain about problems they have with a business. For example, if your luggage gets lost by an airline company, you might tell an airline employee:

This is totally unacceptable!

This phrase sounds formal, but it's also a very strong criticism, so only use it when someone has done something really wrong and you're angry with them.

where I come from

You can use the phrase "where I come from" to talk about differences between your home town, region, or country and the place where you are now:

Where I come from, people say "Excuse me" when they bump into you.

People usually use this phrase when they're complaining about things that people do, which are considered rude in the place that they're from. It's common for people from small towns to say things like this when they go to a big city.