Adding fields, account registrations and editing profile
This is part of Profile2's interface design; different profile types (created in admin/structure/profiles) are presented as separate submenus on the user edit page. 

If you want to work with the constraints of its interface, you can create profile type for each group of fields that you feel should be edited separately. If you feel like a field should be part of the main user edit page, you can add it to the core user entity (admin/config/people/accounts/fields). 

As far as combining profile2 forms into the user edit form, Profile2 does allow you to embed profiles into the registration form (via its Show on all user account registration forms. option) but not the edit form. For that, there is the Account Profile module.


  Profile2 by default creates an additional tab for each new profile
  assigned to a user. Alternatively the submodule "Profile2 pages"
  provides a separated pages for viewing and editing profiles.