Dear Lucy,
Your new post is excellent! (Lucy's post can be seen at the end of this message.) You can be proud of yourself. :-) Keep on doing what you have learned from now on. You have the foundation now that will let you communicate clearly with others.
You said how much you admire those "who can write long passages, and who can show their ideas." Here is another English lesson for you about that. When you have something to say that needs a long article, that is the time to write a long article. If what you have to say only has one or two slight points, then it needs to be brief and to the point. Don't ever puff up an article with fancy words, when short ones would be better. Don't ever puff up an article about a simple little subject to make it seem more important. Some of the best English writing of all time is very clear, and only seemingly simple.
There are people of many ages and levels of education here. People write about what they know, and what interests them. There is so much writing here now about new loves and lost loves because we have gained many newcomers who are students. Romantic love is what they experience deeply at this point in life and it is deeply moving to them, so they write about it. Our lawyer, Dove (Cobra) recently wrote a fascinating series about a shipment that had to be help up in China. That sounds like a dry topic, but her experiences made it very interesting. David is writing about wild animals. When you read someone's post you may think of a reply. One young fellow here recently wrote very feelingly about his sports experience.
Think what you feel strongly about and see if you can write something about it.Maybe it will be about a tree you admire as you pass by on your way to school. Maybe it will be about your dear old childhood doll. There are topics everywhere when you look for them. :-)
Warmly, and with best wishes, Mary