i accedently disscconected it while it was SYNC and then i pluged it back it and then it always neds to update whenever i start it up and then sometimes it freezes also i can't add or delete anymore songs
Try formatting your player on either MSC/MTP mode. It is recommended to format on MSC mode as long as you can access the menu of your Sansa. The player encountered a corruption on the process of synchronization thus affecting its functionality. Formatting will erase every file that you have on your player including file corruption.
Try also checking for updates of your player's firmware after formatting it.
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