Keep training, get a coach and watch videos.
Spin and power is to different things and is somewhat the opposite. The more spin the less power. Hard to get a shot that is both powerful and spinny because spin is slow.
For spin try this.
Close the angle of the racket so you hit over the ball
The spin comes from the arm, the forearm so you need to accelerate with it. Have it extended and relaxed and snap it together.
Try to hit the ball thin and fast.
Sidespin is not necessary.
Try that! The best would be if you posted a video. Would get most help that way.
Excellent for the OP purpose!
Though I'd like to make a small comment regarding speed and spin.
Flat smashed balls are fast and direct, but they experience progressively growing negative acceleration and they loose speed after rebounce.
Aggressive well top spinned balls may come out of the bat with slower speed, but they experience less negative acceleration. When a top spinned ball start to fall the more spin it has the less is the negative acceleration and the shorter it tends towards the table, because the top spin rotation produces less air pressure beneath the ball. When a well top spinned ball hits the table it rebounces with higher speed than its speed at the moment of impact. The faster and spinnier the ball is, the stronger all these effects will be. Its all physics. At some point a flat smashed and a spinned ball would have same speed with the same energy applied.
In my personal experience the fastest balls I've ever done, are those with extreme top spin, though I can't say I'm good enough to do it on purpose, it just happens from time to time, its really very difficult and needs a lot of experience.