미세먼지관련 경험 입니다. 첨삭좀부탁드려도될까요??

in fact i had never thought about micro dust before.

=>have pp인지 had pp 인지 헷갈리네요. 표현하고자한 문장은 '나는 이전에 미세먼지는 경험해본적이 없다' 입니다. 

but these days I realize that fine dust is terrible

anyway in korea the news of fine dust have been issue among people

micro dust usually is derived from china's factory

and negatively affects people's health

many people in korea have said they are negatively affected by micro dust

=> '많은사람들이 그들이 미세먼지에의해 나쁜 영향을 받아왔다고 말해오고 있다.' 이렇게 표현하고싶은데 

     앞에 have pp 이고 뒤에 문장은 현재형으로하는게 맞나요??

my friend also say that they have affected

=> '내 친구들 또한 그들이 영향을 받아 왔다고 말하고 있다.' 이렇게하고싶은데 이문장은 감이잘안오네요.

but I haven't have experience of being affected by micro dust not long ago

but when I went to 서울 last month I realized that micro dust is serious problem

it was when I were going to 서울 to meet my friend

at that time it was a cloudy whether and I simply thought that it maybe rain

however when I get off the bus in 서울

I felt thirsty and blocked

also I kept coughing

I looked around and realize that many people were wearing masks

since that day on I kept coughing and felt blocked for a while.

from this accident I learned that I should always check micro dust index and

take a mask when this index is high 

문장이 길고 배움이 모잘라서.. 잘모르는 부분이 많은데 첨삭한번만 해주실수 있을까요??