Since you are new to WordPress, I suggest you to do some study on basic stuffs on posts, types of posts and queries related core functions. It will be quite useful for you.
And, to maintain the profiles of users, you may go for BuddyPress plugin. Later on, you may work-out on the custom post types with buddypress and achieve the quiz functionality you want to.
For custom post types, either create it manually through functions.php for which you need to study post_types and WP core functions. An alternate for the same could be a CPT (Custom Post Type) plugin. You may checkout their respective documentation files on how to use them.