I'm not sure what you're describing here. If you mean when you tab on one of the thumbnail pictures, the full-screen version has the semi-transparent black bars at the top and bottom containing control icons, if you tap the picture they should disappear, and will remain hidden as you scroll through your photos. Or is it something else you're seeing? If it is, please post a screenshot (press the power and volume down buttons at the same time to capture then attach in a post here from the mobile app).
Dan Galaxy S9 SM-G960U on Xfinity Mobile + Gear S2 Classic