if I change site with local devdesktop it will not change anything with my live site?
Normally there is nothing to worry about. Some advices:


make sure that you are working on a local database and not producction.
Sanitize your database (users + passwords) or use reroute email to ensure that your site does not send emails from your local environment.

drush sanitize




  Reroute email: This module intercepts all outgoing emails from a Drupal site and
  reroutes them to a predefined configurable email address.
  
  This is useful in case where you do not want email sent from a Drupal
  site to reach the users. For example, if you copy a live site to a
  test site for the purpose of development, and you do not want any
  email sent to real users of the original site. Or you want to check
  the emails sent for uniform formatting, footers, ...etc.