Your WINDMILL is built in the same way as these wind turbines, two blades on an axle that is attached to a base.
These large wind turbines are complex engineered machines, but your windmill has also some engineering and physics principles that you might like to know.
The blades are set at a PITCH by cutting two slots in the wooden center piece at an angle with the axle. By turning the blades one turn and let them in your mind “slice” through the air, they make a spiral movement, like a propeller on a boat. The distance traveled is the pitch.
The blades of real wind turbines have a different pitch at the base than at the tip, with the largest pitch at the base. Also the base of the blade is much wider than the tip otherwise the fast moving tip would break off because of centrifugal action and when turning the base carries most of the centrifugal force, therefore they have to be strong.
Centrifugal force develops when you swing a ball or other object around at the end of a rope you feel the ball pulling away, it only moves in a circle because you hang on to the rope while you swing the ball around.
Have you seen figure skaters with one swinging the other around? That is the same thing.
Lots more to learn, but that is for another time and place. Have fun!