I got 29 on writing and 24 on speaking, first try. Other things that you might want to look at when you write is the flow, I mean your entire passage should have have good flow that makes it easy to read, maybe you should pay closer attention to transition between paragraph and try to use different words when you highlight the reading passage (not just repeating the exact same sentences/words with the ones in the question).
If you read my debrief in "Just finished my TOEFL" part, you can see what I think I did wrong and what worked for me. Good luck to you !
Edited to add: another thing that might improve your writing skills is reading newspapers or magazines, or even books. That way you will get a sense on how to write English passages.