There are many applications available that improve your concentration and mental agility; but one that does that and improves your speaking and writing abilities as well, there is only one, and it's called Elevate - Brain Training.
With just a few minutes a day, for a couple of weeks, you'll be able to avoid spelling mistakes that you have been making all life, read a lot faster, and understand the content in a much clearer way.
The application is made up of 16 fun games in which you can test your reading comprehension and concentration; the results will be recorded on a database that will show your improvement over time.
In Elevate - Brain Training you can customize the exercises you take, and each day tackle the challenges that will help you improve your abilities and make progress.