"Operating System Is Modified In An Unauthorized Way" when updating to Galaxy E7 Root

Some days ago, I had rooted by new Galaxy E7 for using rooting features. But now, I am unable to download updates from Samsung using Software Update. Please tell me what to do. I have already tried unrooting the phone using superuser and then tried to update the software but it didn't worked. Now, please tell me the following things:

1. How to unroot Galaxy E7 nicely using odin?


2. How to update it to latest firmware available using Software Update

Thanks for your time.