Unhappy [Q] HTC desire 816

I recently bought a desire 816 mobile
I'm happy with everything in the phone except that all the pictures from 9gag and tumblr apps automatically are saved to my gallery ?
what should I do ?!

I did a little research..
I found that its called the nomedia file problem ?!
some told me that I can fix it by creating an empty text file ! the problem now is
I dont know how to create text files on HTC desire 816 & I dont know where to create it ?!
please DO help me because I'm losing a lot of important content by mistake ><