Hey @jens,
Firstly, great job! 
I really appreciate how you’ve shared your thought process and figured out which charts work best. Do you have a background in analytics? Your structured approach and the way your exploratory analysis led to more questions is really engaging. This is exactly what got me into data visualization a few years back. It’s always interesting to see how different people can interpret and visualize the same data set in unique ways 
Don’t worry about not creating a dashboard. It’s not obligatory for this exercise as mentioned by @adamschroeder! Honestly, making the chart is usually the toughest part. Adding it to a dashboard is much easier. If you haven’t come across Vizro, it’s a tool that could simplify that dashboard creation step for you. It’s built on top of Dash and it’s what I’ve been using in my submission above 