Does writing improve ones english?

I’m here to improve my english. More particularly my speaking abilities. Unfortunately, I can not speak here, instead I will resort to typing what I would have said if I’m spoken in english. I will type as fast as one should be speaking. I will not pause for backspace or delete. So you’ll have an exact idea how well, or (bad) my english is. When writting I usually pause a long time, and I don’t even write continiously. Usually I write the first sentence, then I’ll write in the last sentence. Then later on I’ll insert the middle sentence. I even edit what I have written after a minute or two. That is not allowed when speaking English right? So I will really just type what comes first in my mind.
My downfall would be prepositions and a few sentence formation. Please feel free to comment and improve my english.