"As I am working quite a lot usually 6 days of week with around 10 hours per day",and not one word German used, my!! !
You really must get into a group of German speakers, you need also the German social contact too learn it properly
look to the VHS for an advanced course, "not for integration ", it won't come to you.
International School Düsseldorf, situated in Kaiserswerth, excellent, my ex-wife worked there as Teacher-assistant,
she said that the care and consideration for all pupils was to the utmost priority of the school.
or a separate water reservior for the shower, where the water is treated with lime-juice( excellent de-kalker),
and cheaper than market brands, especially as the water lies in the tank for a while before use