For changes on the code base you should always use a child theme. To update your theme you only need to:

  1. Do backups
    1. Filesystem
    2. Database
  2. Set wordpress to the maintenance mode
    1. Create a .maintenance file in your installed wordpress directory
  3. Delete the themes folder
    1. You can find it on your installed wordpress directory in /wp-content/themes/pinpossible
  4. Upload the unpacked folder to /wp-content/themes/
  5. Reset wordpress to the productive mode
    1. Delete the created .maintenance file in your installed wordpress directory