Problems upgrading to el cap on 2009 macbook pro

[deejaybabyboy]

Hi guys, couple of months ago, i got my iphone 7plus and had my old macbook pro 2009 model... when i tried to connect my phone it did not work so i called the tech support for help... he gave me a link to upgrade my macbook to el cap so everything will run smoothly but when i download the upgrade and install it, even though i have enough space for the installation, i am getting an error message and its not even reverting back to its old self! I am a dj and all my music and composition is now stuck in there that i cant even get a backup of!! How can i revert my macbook to its original state?? Please help... thank you