Will I loose this content or the content will be saved? I'm new in drupal. I have one site that is running on drupal version 7 and now needs to be upgraded. My question is: I have big content in this site, after the upgrade will I loose this content or the content will be saved?
No, you will not loose any content after upgrading the site. But before upgrading the site please take care of the following things.


Back up your database. 
Back up your code.