Good day! "Изучающий" - is participle, not verb. It uses, when you whant to show a sign of the subject through the action. In this example action is "изучать". "Изучающий" means "somebody, who learns something". "Изучаетесь" - plural verb, adressed for some group. Postfix "-сь" means, that action must take place over yourself. I hope that I've answered for this question.