Unable to hide pictures and videos stored in external memory in Samsung A5 2016

[AC Question]

I tried few apps to hide the videos and photos are stored in external memory card in my Samsung A5 2016. For mean time it's been hided and after a short while it's appearing again in the gallery. When I'm using Samsung Knox, it's consumes the internal storage. Is there any app or setting to hide this? Also I cannot find the private mode in this.