How to get rid of hard water stains on shower doors?

This might help Debra

https://www.hometalk.com/diy/clean/bathroom/how-to-remove-hard-water-spots-naturally-29175381

One half grapefruit, coarse kosher salt, salt grapefruit, scrub glass in circular motion, resalting & using new grapefruit as it wears away! No vinegar smell, nice citrus smell & easy to do

20 Mule Team borax on a damp sponge. Works amazing!

I have 2 suggestions for you.

1- any cleaning product with bleach in it works well to dissolve water stains. Using a spray bottle spray the glass door. Next take an abrasive sponge and gently scrub away the stains.

2- a more gentle technique is to use "Dawn" dish soap to wash the glass followed up with a spritz of vinegar and water to polish the glass to a shine.

I do this professionally. Use a soap scum remover such as scrubbing bubbles or lysol power bath. Spray it on, let sit for several minutes, and then gently scrub with a nylon scrubby. Rinse. If necessary, repeat immediately while it is softened. Once you have it shiny again, just spraying this soap scum remover, let sit and rinse weekly should keep it from getting buildup