I have been in Nanjing for 4 year since 2005.
I came Nanjing in 2005,I have been here for five years
I came Lanjing in 2005. I have been here for four years.
I have been in here for four years since I came Nanjing in 2005.这里用现在完成时比较能表现出你现在的状态。
I came Nanjing in 2005,I have been here for four years
I came to Nanjing in 2005,and I have been here for five years .