hi need help with my iTunes when i sync my phone it says cannot sync error -50??

Hello, martinqaqish.

Thank you for visiting Apple Support Communities.

Try forcing all applications to close in multitasking and power cycle the device. Once this is done test syncing your device.

iOS: Force an app to close

http://support.apple.com/kb/ht5137

iPhone, iPad, iPod touch: Turning off and on (restarting) and resetting

http://support.apple.com/kb/ht1430

If the issue persists, try the steps in the article below.

"Error -50," "-5000," "8003," "8008," or "-42023"

These alerts occur due to timeouts or conflicts trying to write a file during download.

If you encounter this issue while accessing iTunes Store:

See iTunes 9: "One Moment Please" or "Error (-50)" message when accessing iTunes Store

If you encounter this issue while while downloading something from the iTunes Store:

Delete your iTunes Downloads folder, located in:

Mac OS X:
 ~/Music/iTunes/iTunes Media/Downloads Note: "iTunes Media" may appear as "iTunes Music. Also, the tilde (~) refers to your Home directory.

Windows Vista:
 \Users\username\Music\iTunes\iTunes Media\Downloads\

Windows 7:
 \Users\username\My Music\iTunes\iTunes Media\Downloads\

Windows XP:
 \Documents and Settings\username\My Documents\My Music\iTunes\iTunes Media\Downloads\

After locating your iTunes Downloads folder:

1. Quit iTunes.
2. Delete the Downloads folder on your computer.
3. Open iTunes.
4. Choose Store > Check for Available Downloads.
5. Enter your account name and password.

If you encounter this issue while while downloading Digital Copies using Windows:

iTunes: Advanced iTunes Store troubleshooting

http://support.apple.com/kb/ts3297

Cheers,

Jason H.