Take a look at indoorco2map.com and you will find plenty of places in Germany with bad air measured in a crowd data collection effort. Most notably doctor‘s offices are often very bad. Many supermarkets too. Schools are not well measurable this way but academic research shows they often are at 2000-3000 ppm or even higher. (Disclaimer: I built the website/App)

when i read the article i thought that maybe this is where german ingenuity comes from.

but then germany hasn't been doing so well lately, and people who do most of their work outside should also be doing better...