This is a fun movement to learn, the kettlebell windmill.
Many people would look at this movement and say, “doesn’t that hurt your back?” The answer to that question is, most movements hurt your back when you don’t do them correctly, that’s why you must look at exercise and training as skills to learn so you slow down, get good at them, and then progress.
Have fun learning this one. Go light and do it right, heck, you don’t even need weight when learning the kettlebell windmill. You’ll discover soon enough that your mobility will be quite challenged and to move safely in this pattern, it needs to be done with light resistance.