Hoping for some technical advice pretty please... Recorded a video of DS performing for school. He tried really hard and video is perfect except for an annoying shadow on the wall where I'm waving my hands about in the background trying to help him stay in time. 
I'd love to be able to crop out the background and superimpose the video on a nice plain non-distracting background. Can anyone help please?? I tried an app called kapwing but the file size is over 250mb so it won't upload!