Go to gallery app, hit the 3 lines at the bottom right corner and select "settings". In the settings menu go to the bottom and hit "about gallery". On this page you will see the word "Gallery" at the top and just below that the word "Version" and a string of numbers after it, continously tap the string of numbers until you see the words at the bottom "gallery labs is now enabled". Now go back to the previous page into the gallery settings menu, Scroll all the way to the bottom and you will find the option "gallery labs". Go into it and turn off the feature "Filmstrip in viewer" and the restart gallery app. You should now not have to open the video player manually anymore When you click on a video.
