Hey Tim ,the serve is looking good already! I would say when trying to get topspin don’t actually think about adding topspin to the ball on purpose, if you just follow around the side of the ball with your bat you will get it anyway, rather than lifting the bat upwards too much to get topspin. This will make it much harder for players to read the spin and see what you are doing when you also master the backspin one together with it as well.
You have a good body movement and action, just also think about getting the first bounce on your side of the table in the same place all the time, one for consistency and two so again it’s two bounces and hard to read as well. With what you are doing here I feel if you keep training this and following the course you’ll have some very good serves!
