Nice sentence! Here are easy corrections and a short explanation.
Best simple correction: My room is my kingdom for playing and sleeping.
Another good option: My room is my kingdom where I play and sleep.
Why?
- My room is my kingdom — that part is perfect. It means your room is special.
- We change to play and sleep to for playing and sleeping because 'for' + ‘-ing’ words (playing, sleeping) sounds smoother when we talk about what we do there.
- Or you can say where I play and sleep to show it is the place you do those things.
Try saying both corrected versions out loud and pick the one you like best!