1. Take care/ Have a good day/have a good one
When you are gonna hang up or leave some places (like a market, your office, classroom, etc ), normally you could say take care or have a good day before you say bye. It’s also applicable when you are gonna get out of a car/the taxi or say goodbye to your frinds/family.

2.Thank you/ I appreciate it
It might a little bit strange cuz it’s sort of different from the situation in China. Here when you are gonna take off the bus, the majority of people would say thank you, thanks or I appreciate it to the bus driver to show their gratitude when the door opens.

3. Sure/Of course
Well, actually not a lot of people say “certainly” nowadays, most people use sure or of course and there is a slight difference between the two phrases. For example, when someone relies you with sure, like “do you want a cup of coffee?“ “sure”, it means he or she is very glad to do that. About “of course”, people say that when it’s something very obvious or something that you think someone probably already knows or will not be surprised about, like “what else could it be?” like, ”I will, of course, attend that class as we planned before.”

4. Pale/dark.
Don’t use white or black to describe people’ skin color. It’s not appropriate at all. You could use pale or fair when someone has a light skin while dark or tan when the skin color is not that light.

5. No problem.
I think you guys are pretty familiar with that phrase when you wanna reply to “could you help me” or things like that. However, apart from that kind question, “no problem” is also used when someone says thank you to you. Under that circumstance, it shares the same meaning with “you’re welcome”.

6. –ish/-something
“ish” is usually added onto the end of a word or phrase as a stand-in for "sort of" and "kind of". Like, “do you love that movie?” “well, yes..ish.” It means you don’t actually love that movie. “ish” could means “give or take a time period” as well. For example, “I’ll come to you house at 12-ish.” Which means you gotta give or take one hour.
In terms of “something”, I will just give your guys some sentences. “Do you know how old that girl is?” “ well, I guess maybe…10-something?” It means you think that girl is around 10 years old. Or “you want a banana or something? ” so you could have other choices.

7. I didn’t follow.
When you have trouble understanding someone, which is actually really normal even for some native speakers, except “I beg you pardon?” “can you repeat that”, you could also say “sorry, I didn’t follow” to tell him or her that you don’t really get his or her point.

8. I was just wondering if …. (past tense)
It’s an informal way to ask somebody about something. You could say “I am wondering” as well, but using the past tense is more polite actually. It’s used to mean “I would like to know…” in a polite way. And the past form could accomplish the extra politeness. And the past form should be maintained in the rest of the sentence.
For example,”I was wondering if you wanted to have dinner with me.”
Btw, “Would you mind if…?” works in the same way.

9.Are you available tomorrow?
People use this frequently when they wanna ask someone out or make appointments. It’s more formal than “are you free tomorrow?” And it’s not just oral English, you could put it in your email as well.

10. I can‘t make it.
It’s used when you are unable to do something. Like when somebody turns to you, asking for some help, but you can’t solve that problem either, you could use this sentence. Or, if somebody asks you out, but you already have other plans, you can say “Sorry I can’t make it” as well.

Have a good day. :)

12. Shoot
Apart from the meaning of shooting somebody or something, “shoot” also means “go ahead”. Like, “I got something for ya.” “Shoot.” And it also means “shit”, but just a little bit more polite and less approaching.

13. No worries
I mentioned “no problem” before, and “no worries” actually has the same meaning.