Keep a small rubber squeegee in the shower. Spending thirty seconds wiping down the walls and glass doors after your shower removes the water and soap residue before it can dry and harden.
Rinse the area thoroughly with warm water. Use a microfiber cloth to wipe the surface dry and inspect your work. Repeat the process on any remaining stubborn spots. For Natural Stone (Marble, Granite, Travertine) clean soap scum
There are numerous commercial bathroom cleaners formulated specifically for soap scum and hard water removal. Look for products containing phosphoric acid or sulfamic acid. Always wear rubber gloves, ensure the bathroom is well-ventilated, and follow the manufacturer instructions precisely when using these strong chemicals. Keep a small rubber squeegee in the shower