Unwanted Pictures Showing in Gallery, how can I get rid of them for good?

[AC Question]

Unwanted Pictures Showing in Gallery

While I'm facebook chatting if anyone sends me a picture my phone automatically saves it and adds it to my gallery.
If I delete them sometimes the next day when I turn on my data they all resave and show up in my gallery.
Thats any photo or gif someone sends through Facebook messaging. I'm deleting like 40+ photos/gifs per day.

I have a Samsung Galaxy S6

 

[IAmSixNine]

I dont use the app but my guess would be since they still reside in the chat the phone is saving them again when your data reconnects and the conversation in the facebook chat app refreshes.
I would suggest finding the directory the app uses and put .nomedia in it so the gallery app wont find them.
OR maybe in the gallery app limit what your viewing.