Writing is a great way to improve our language skills. At the exchange at LingQ you can have your writing corrected by native speakers of the language you are learning.
Don't expect that having your writing corrected will fix your grammar mistakes. Research consistently shows that writing correction is not effective in correcting mistakes. However, just the act of writing, in the knowledge that someone else will review what you write, forces you to put a lot of effort into looking up words and grammar as you construct what you want to say in the language you are learning.
When I correct English I find that "use of words" is by far the most common area of error, rather than particular points of grammar. That is why I would only ask a native speaker to correct my writing. Usually it is only a native speaker, or someone who has lived in the country where the language is spoken for a long time, who has that natural sense for standard usage.
What I find most useful when I get my corrected writing back, is to save the phrases and patterns that my corrector has used to replace what I wrote, to make it more natural. So the writing correction report becomes content for me at LingQ!