Can you explain me the grammer

It's very difficult to explain it! but, I am going to try.

그러게 is like "I agree with you but I didn't do that" ="I should've done that.."

For example,

A :Hey, you wanted to get some coffee. why did you not buy coffee?

B : 그러게... 

Another example,

A: you had to be quiet in the public place.

B: 그러게...

but, 그러게 is informal so, you should use this word with your friends.

Can you explain me the grammar 제 취미는타는 것을 자전거이에요. Why can I say 제 취미 자전거이에요? CAn you give me example please?

The correct sentence is 제 취미는 자전거 타는 것입니다. or 제 취미는 자전거 타기예요.

It means My hobby is riding a bicycle.

My hobby is = 제 취미는 ~ 입니다.

riding = 타는 것

bicycle = 자전거를

=> 제 취미는 자전거(를) 타는 것입니다.

For example,

My hobby is reading books

제 취미는 책(을) 읽는 것입니다. = 제 취미는 책읽기 입니다.

My hobby is watching movies.

제 취미는 영화(를) 보는 것 입니다. = 제 취미는 영화보기 입니다.

In this sentence, It doesn't matter whether you write '을 or 를' or not.

How can I say in Korean "Get away from here(I don't want to see you)" in slang language and in formal language.

꺼져!! is slang

저리 좀 가주세요!, 비켜주세요! is formal 

It is not perfect. I'm not a professional teacher but, I wanted to help you.

Have a nice day!! :)