I would like to learn how to use better English expressions(27)

Valuable experiences. Adults always say that experience gained from life can't be replaced with anything else. After going through this incident, I felt as if I became more mature. Time flew so fast (1). It seemed that I kept myself busy with my studies and works. I even got a girlfriend. This is why I didn’t have time to think of the friend (2).

I would like to learn how to use better English expressions, so I hope you can help correct errors in my writing.

1). Where I come from we say multiple things for this phrase. The one that sounds most natural to me is: Time flew.(Nothing else just those two words) Another one that is used more when speaking is: Oh, how time flies. 

2). It is a little confusing as to why you put the in front of friend. Did you mean "my friend", because otherwise it sounds like you are foreshadowing a future event.

If you have any questions feel free to ask!

는 would go after "I" because 나 ends with a vowel (in this case 아) but if you wanted to say "Tim" (Like the name) you would use 은 because 팀 ends with a consonant (in this case ㅁ)I hope that helps.

They basically mean the same thing, Example: She wore the appropriate clothing for the event She wore the proper clothing for the event She wore clothing that was suitable for the event 1 difference is appropriate and proper can be used to describe behavior, while if you use suitable it might sound awkward. One thing I realized in talk is that proper is used in more formal talks than the other two. And to answer Hassan's question reasonable could be used the same as the others, but not always. Reasonable is usually used to describe something is close unlike the other words are used to describe something that is exactly right/wrong. Ex: She wore reasonable clothing for the event It sounds as thought she didn't dress exactly like she should have but she still dressed well. I hope that helped, if you have any questions feel free to ask!

We usually feel bad that we didn't know. 1st reason is because we probably didn't go to the funeral and pay our respects. We also just feel sorry because we made them remember something they might not want to. (Because it's difficult to get over a loss of someone) If you have any questions feel free to ask!

바 비 because 밥이 the second b/p sounds more like an m in this case. So use 바 비

For Korean you really should learn Hangul first. Then I would learn basic grammar rules and become comfortable with the different formalities.