Why Sebastian does not know how to write?

I think the hardest part to write an essay is the vocabulary because I feel that is not enough to express what I want to say, also I do not know a lot of academic vocabulary and my words are in the basic way but I know that is a problem that I only can fix practicing and practicing.  Another problem that is hard for me is brainstorming because sometimes I do not know more ideas about the topic that I am writing and I do not know how to organize the ideas correctly. Also another problem in my writing is that is really hard for me is to focus in my topic because sometimes I am writing about a topic and I finished writing about another topic and I know that I have to keep writing on my topic and focus on it. In addition I think another problem that I have is spelling the words, because I know how to say them and I make a lot of grammatical errors in my writing.  Finally, I think another problem is when I am trying to express something I feel that is not enough and is not what I want to write.   Sebastian