I forgot to add how to clean the glass shower doors. Once a week get some liquid gel bleach cleaner. Use a slightly wet sponge that has a scourer on one side & squirt a little onto the sponge. Clean from the top to the bottom of the glass. You can also use this on the tiles in the shower. Leave for 10mins. Don't forget to clean any sliding tracks too.Then get an old cloth nappy or face washer that is dry & polish. No need to rinse.
For hard to get off scum use a magic eraser or a steel soap pad. Some glass will look dull if the dirt has etched into the glass. You cannot get that looking 100% clean.