How can I use CiviCRM for registration, login, forgot password pages on Wordpress?
The registration part is quite straight forward and described in the manual at https://docs.civicrm.org/user/en/latest/organising-your-data/profiles/#wordpress-user-account-registration-option. The profile allows you to collect additional information and populate existing or custom fields.
The login and forgotten password screens are WordPress pages so you can't replace them with something from CiviCRM, but they can be customised sufficiently to make them look consistent and a bit of googling is probably the best way to find out how to do what you want.