Why I can't add anything to my homescreen bottom row on Samsung Galaxy S3 Neo ?

[AC Question]

I think this problem may have started when I recently had a problem with com.android.systemui after updating to the latest google now. Uninstalling google now updates fixed it but as I was looking for ways to fix this problem I also have reset app preferences & after that my homescreen bottom row of apps disappeared & now I have only a white camera icon on the left & Apps icon on the right. Whenever I click Apps nothing happens although I had no problems before & it used to open up just fine. When I try to add apps to the bottom row I can't do it. I long click an app & drag it down & release like I'd do it normally but it just returns to the same spot from where I dragged it. I tried deleting the white camera icon on the left but I can't drag it. Someone please help !