Well, more information would be needed to help provide any sort of assistance. What is the video format? The FPS of the video (24, 30, 60, other)?
Also, the forums are not really designed for reporting bugs or issues with Godot, as developers are not that active on the forums and GitHub has an issue tracker designed specifically for users to report issues. I would suggest searching to see if there is an existing issue with slow VideoPlayerNode performance on Android and if there is not, making an issue on GitHub explaining the situation.
