Is it safe to drink tap water in Germany? [duplicate]

I just arrived in Germany for the 4th time. I made tea in break of the work meeting, and at the very end of it, I found small solid pieces... I thought that the cup was too old and maybe was starting to lose its "material". A guy told me that this because of the water being "too heavy" here in Germany, and he doesn't drink it, but filters the water through a machine, and then drinks it.

During my first trip, I asked if it is OK to drink tap water in my hotel, and they said yes, but we don't drink it, we buy mineral water from the market. And from all the people I have asked here, this is what I get as an answer, more or less.

My mother told me that the water in Germany is not drinkable, because it has too much iron. I think here they call it kalk, which seems to be some metal in any case.

The knowledge of my mother is likely to be outdated, and while searching the Internet, I see that the situation has changed across the years, and that now it's safe to drink tap water, which contradicts what people say in real life. I am very confused.

So, is it safe to drink tap water in Germany? Nobody gives a boolean answer which makes me worry! If area matters, we travel in Munich and nearby towns, all parts of Bavaria.