Hey Hamza, ok so this could be a for a few reasons, as you said because the ball is a bit slow, but it could also be if your shots are landing too short on the table and not near enough to the opponents white line which makes it much easier to play an aggressive shot against you. So the key things to try here are making sure you get a good acceleration through the ball on contact, keeping a relaxed swing as well.
Aslo with the backhand being sure to use the wrist well to release forwards and through the ball which will add speed tot he shot and also help you get better depth on the table as I mentioned. The last thing is making sure you are using your legs and body which will help you generate power and enable you to keep your arm more loose as it’s not doing all the work.
Hope this is helpful and let us know how it goes!
Tom 🙂
