What's it made of? Acrylic, ceramic tile, fiberglass, faux marble...?
Lysol Power Scum cleaner in the blue trigger spray bottle with a Magic Eraser or a scrub brush.
If a bad build up, Lysol Lime & Rust Remover Toilet Bowl cleaner, comes in a black squirt bottle. Scrub with Scrub Daddy or Mr. Clean Magic Eraser.
Wet & forget shower for a slower, no scrub solution. You can use 2x a week to accelerate the cleaning process then once a week to keep it clean.
I use vinegar and water - about a 50/50 mix with a few drops of Dawn or other dishwashing liquid. For really bad spots, I might scrub it with a paste made with baking soda and water first. Vinegar will remove hard water spots and leave your shower sparkling. Wishing you the best.
It is one of the easier cleaning jobs! Here are some ideas for you.
I use an inexpensive spray cleaner from Dollar Tree that you spray on your shower walls and wipe off, and it smells so clean. If you want to deep clean your shower, here are some ideas for that.