Cannot close videos or photos when in whatsapp or facebook on s7 galaxy

[AC Question]

When I go into WhatsApp and want to take a photo, if I don't send the photo I can't close the camera. Therefore if I click on the camera and then decide not to send a photo I cannot close the camera and go back. Same problem in facebook. When I click on a link to a video from my wall, after I finish the video, I can't get back to my wall. There is no cross in the corner to close the window