Cut out video compositing practice

I originally wanted to composite my video into the world but I didn’t find the green screen and the low quality video crashed the after effects down. So I just find the black cat video online and composite it with the shot of UE.
I used roto brush tool to cut out the cat video.
To make the cat seem to be more fit into the scene, I adjust the level of it and duplicate one to add flip effect and fill with the similar color with box’s shadow so the cat will look like lying on the floor for real.