Sorry, I didn't know the "After seven days, the post can no longer be edited." policy. I completed my work again here(https://steemit.com/ubuntu/@leobcyang/1, https://steemit.com/ubuntu/@leobcyang/2, https://steemit.com/ubuntu/@leobcyang/3, and https://steemit.com/ubuntu/@leobcyang/4). And it is NOT an "introduceyourself" post. I should publish a real "introduceyourself" post a few days later. Thank you.