How to play table tennis backhand?

First, your fingers are too straight, occupying a large area of the racket face. Tilt your fingers up a little (as shown in the picture).

Second, the ball board is too deep to eat the ball. When hitting the ball, always hit the ball with the middle part of the ball board or the heel part of the middle part. Adjust properly and try to hit the ball with the side part of the middle part.

Third, practice more. It's definitely not suitable for straight back hitting at first. This can be solved by playing more.