Black Stripes appears in video both side left and right because you haven't edited the video. I use Kine Master pro version in my Android mobile. We have to crop the videos to fit the full landscapes screen to get the best result. Secondly, we have to save the video in 1080p format to give the quality of our video HD. You can go for 360p, 480p, 720p only if you're creating a video to upload on YouTube.
Download the kine master or pro version. In free version, the water mark will be displayed on your video. Once you download the app, start and choose empty projects, browse the media video file you want to edit, select it, and once the video is on the editing layer, click the drop down option on the right panel by choosing the crop option. Adjust the ration by cropping on both side or that contains black stripes. Save the video and you're done.
Hackers never learns but always wins!