How to migrate nodes from a dev site to a production site? I have a staging site and a production site.  

For an error some nodes was updated on the production site and now I have to update it but, if I will do that I will lose the production site changes.

What is the best [and faster] approach to migrate some nodes from production to staging before migrate staging to production?
Sounds like Node Export to export your nodes from dev and then re-import them on your live site.

Node Export provides several ways to export nodes:


Through a tab that appears on the node page.
Using update options on the Content page.
In a command line using Drush.
Using the Features module.
Using the Views Bulk Operations module.


and the Node export package comes with the following formats:


JSON
Drupal var export
Node code
CSV
Serialize
XML