How can I clean and regrout my shower?

It would be much easier to make some suggestions if you posted pictures showing the color and condition of the grout. What you use to clean the grout often depends on the color of the grout. If ,after cleaning, the grout still needs replacing , it would be better to hire someone who does that work.

The best thing to do when you have grouting done is to make sure that the grout is sealed from the get go. I seal ours at least once a year and it stll looks like new after 8 to 10 years. It takes just a minute to make sure that I dry the tiles to prevent water spotting and to avoid mildew.

Some of the new grouts contain compounds that resist mold and mildew, but I was told that sealing is still a desirable thing to do because resistance is not total protection.

Unless it's colored grout, I Use Tilex. Let it sit a bit then use Soft Scrub and a scrubby.

Be sure to seal once cleaned.

To remove grout is very tedious, you have to dig and grind it out without chipping the tile. Another option is to paint the grout with oil based paint.

Clean grout

https://www.hometalk.com/search/posts?filter=clean%20grout

Remove and replace grout

https://www.youtube.com/watch?v=DytsjSHlCWU

https://www.diynetwork.com/videos/removing-and-replacing-grout-0255954

https://www.lowes.com/projects/repair-and-maintain/repair-tile-grout/project

Hi Celeste. I'm Cindy. I clean my grout with a product called Oxi Clean Max Force. Use an old toothbrush to scrub it into the grout. Let it sit for 15 or 20 minutes then wipe it up with a clean cloth. To remove grout, use an oscillating multi tool with a grout removal accessory. If you will be buying new grout, remember that sanded grout is for floors and un-sanded grout is for walls and counter tops. Good luck Celeste.