Once you've completed an exercise, it's automatically sent to our Community. Here, it can be viewed and corrected by students who are native or advanced speakers of the language you're learning.
The best way to get more corrections is to connect with friends on Busuu. When adding new friends, consider connecting with those who speak the language you're studying and who are also learning your language. It's a win-win! See more info on sending your exercises to Busuu friends here.