In a way, yes, but ultimately each has it's own meaning. 언니 is what younger girls use to address older girls that are or like their older sisters. 오빠 technically means older brother but only girls use it for guys older than them. 선생님 is actually what you'd address a teacher as. There are also the terms 누나 and 형.

Hello!

Hi, my name is Jun Ho Cha.
I live in Sejong.
I'm 17 years old.
My hobby is play playing games.
Please give me advice on my english
I would change this to something like "Please help me improve my English." or "Please assist me on my ability to speak English."

Thank you^^

 

Overall, your English isn't bad. There are times when it'd be better to connect your sentences and make more complex sentences but aside from that you only had some mistakes. By sure to capitalize the beginning of your sentences and names (<em>such as your name and the names of specific places like Sejong</em>).

Good job! Keep going~

My recent career

I graduated from Hannam University with a background (I would use the word degree over background) in Convention Hotel Management.

Before graduatied graduating from university, I had took taken a year off and I worked at Lotte Hotel at that time the English idiom "for the time being" sounds better here although you could rearrange this sentence in many ways for it to make sense.

Soon afterward after, managers and captains was turnig were beginning to like me, because I worked really hard, and <em>I could learn so much about the service industry. </em>I'm a bit confused about what you were trying to convey, but I think you simply meant that since you worked very hard, you could learn a lot about the service industry. If that's the case, then I would recommend turning that sentence into its own personal sentence since it's not exactly related to the other two sentences and the sentence may become a run on sentence if that makes sense.

However, I had dicided decided to study English, so I quit my job and took a lesson lessons from at the SDA English Institute in Seoul.

I studied English at the institue for 7 months and came went back to university.

Prior to graduate gaduation, one of my professor had recommended a job in at a hotel for me, and I had interviews at the hotel. Instead I would say "..., and I went to a series of interviews at the hotel"

They offered to me a job, but I really wanted to come to the United States to study more, so I declined and came to America to study English more instead. For this sentence, I would rewrite it a bit because it was almost becoming repetitive and a run on sentence. Personally I would write "The hotel offered me a job, but I declined their offer. I really wanted to travel to the United  States to study more before taking a job there." or something along that line. Your sentences weren't really wrong, I just think it sounds more natural that way.

After I finish my courses here, I will travel around the America and then go back to my country. I will find my a job in there as soon as posiible possible.

 

Your English is really good and I enjoyed reading about your interesting career path up to this point. I also find it amazing that you're doing all of this to learn English. You're awesome, and I hope I helped a little!