Soap scum and limescale are two different problems that usually show up together. Soap scum is a film left by soap and body oils. Limescale is the white, chalky mineral deposit hard water leaves on glass, faucets, and shower heads.
For limescale, a mild acid works best. White vinegar or a cleaner made for hard-water stains loosens the minerals. Apply it, let it sit for several minutes, then scrub with a non-scratch pad and rinse well. Never mix vinegar with bleach.
Soap scum responds better to a degreasing bathroom cleaner and a soft brush, working from the top of the wall down.
Natural stone like marble and travertine is different: acids can etch it. Use a stone-safe cleaner on those surfaces.
To keep the buildup from returning, squeegee the glass after each shower and run the exhaust fan so the room dries out.
If the buildup has been there a while, a deep cleaning from Innato Cleaning Services will get your shower back to clear glass and shiny fixtures. Call (629) 256-5608.