Default ADB Restore - No datas despite being successful

Good evening,

I wanted to root my Nexus 5, so I decided to make a backup of my phone before doing so. I installed the Android SDK and made a backup through the "adb backup -all" command. This was successful - I got a backup file out of this (4,7 GB). After rooting my phone and installing a custom rom, I wanted to restore my files. I used "adb restore" for this. The process started - I confirmed it on the phone - It loaded for about 10 minutes after it shut down with the message that it was successful. The problem is now that nothing have changed - nothing got restored.
What can I do now? Especially my WhatsApp files are kinda important.

Anyone had this problem in the past?

Thanks.