Apple devices take a long time to sync videos and music, and how can I transfer them successfully?

Someone please let me know why Apple devices doesn't sync videos and music in a short amount of time. iTunes was working great and that has been discontinued and a new device is in operation which definitely requires some technical assistance. I have been trying to transfer home videos it took very long time to transfer and two days later they were disappeared.

[Re-Titled by Moderator]

Original Title: Apple Devices not working