I have the same problem, but what solved is using Le Chat SENSITIVE. Look for that, Le Chat sensitive. Also, if possible, install a filter for your shower and replace it every 6 months. An example of a filter https://www.amazon.fr/universel-Cartouches-pression-impuret%C3%A9s-Aquahomegroup/dp/B01M62IRCV/ref=sr\_1\_8?\_\_mk\_fr\_FR=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=25BQ6JHMZBRL4&keywords=filtre+douche&qid=1649614218&sprefix=filtre+douc...
Not the OP, but yep, something like this - https://www.amazon.co.uk/dp/B01M62IRCV?psc=1&smid=A3DLK7VZHLAUDP&ref\_=chk\_typ\_imgToDp
I‘m trying to work out the same issue. I’ve tried this: AquaHomeGroup Shower filter. It makes a change but don’t expect wonders. I just order this Philips Shower filter so still don’t know what to expect but after reading the reviews, I don’t expect much. What I‘m planning to do is combine both of those filters and see what happens. I also bought testing stripes so I have measurable results. Fuck the hard water in Berlin. If this experiment doesn’t work I don’t know what my next step is gonna be.
Im waiting on this one to arrive. Decent amount of reviews and quite cheap, so worth a try.
https://www.amazon.co.uk/dp/B01M62IRCV/ref=cm_sw_r_cp_api_fabc_7JP07RF1CNG4TF81GKQE
If you just want to soften the water in your shower and nothing else, I would consider a product like this sold on Amazon
Found this, may be better options but you can look at the reviews for yourself.