If you no longer want to be the group administrator then you can change it easily. Take the following steps:

  1. Go to the group in WhatsApp, press the settings icon and go to group information.
  2. You can see a list of all persons in the group.
  3. Press the person you want to make administrator. And then select Create administrator.
  4. If you do not want to be admininistrator, you first make someone else administrator. Who can throw you out of the group, to invite you again then. This also works if you leave the group, and then be invited again.

    Note
    You can only make someone else administrator if you are an administrator your self.