Restoring iPhone backup from iTunes taking too long I got a new iPhone today to replace my broken one and I am trying to restore the backup from iTunes. I had around 50 GB of content in my old iPhone.

The remaining time to finish the backup started in 2 hours, and is steadily increasing (to about 27 hours at the time of this post).

Is there something wrong with my system?

I am recovering an iOS 9.3.2 backup to an iPhone 6 (64 GB) on a Mac running macOS 10.11.6 (El Capitan) on a 2013 iMac. I am using the lightning cable to restore the backup, and not over Wi-Fi.
First of all, you need to make sure that you have the latest version of iTunes (Currently v12.4.2) installed on your mac so that it supports the latest version of iOS.
Secondly, you can't restore an iPhone with a later version of iOS (iOS 9.3.2) to an iPhone with an older version (for instance, iOS 8.x). So make sure you've updated your new iPhone 6 to the latest version of iOS which is currently 9.3.3, then try it again.

I recommend you read this link and also this one so you'll get more information.

I hope I could help you. Good Luck.