https://www.feeltennis.net/improving-balance/
This is part 2 of Balance in Tennis and in this video you can learn 4 simple drills that help you improve your balance and stability on your forehands and backhands and therefore gain better control of the ball.
The first drill is just drop feeding the ball to yourself and staying balanced for a few seconds after you've hit the ball.
The second drill is doing similar but while you play. So after you hit the ball maintain your position (or transfer weight) and feel the balance.
In the third drill use a soft ball and place it under your foot and squash it while you simulate the strokes. Make sure to keep the heel on the ground!
The fourth drill is done in the gym on the BOSU ball where you also practice all stances for forehands and backhands.
I also suggest you check out various channels for more complex balance exercises.
Here's how complex is Novak Djokovic's balance training:
https://www.youtube.com/watch?v=lVPP1yJ40VE