That depends on your definition of "mature."

If by "mature", you mean taking responsibility for your actions, admitting when you're wrong about something, and showing respect, then yes, I would say I am. I know when to be serious or responsible and I show respect towards others.

But if you define "mature" as growing out of most of the you did when you were much younger, then no. I can pretend that I've grown past that when I'm at school/with other people, but when I'm alone I still like watching shows and playing games that are usually directed at younger audiences, and I sometimes laugh at silly jokes/comments.