Short explanation for task 6:
If the figure is turned, so it lies on the side, it corresponds to the facade, 20×3 concrete slabs.
The marked squares show which concrete slabs with windows must be counted.
There are 7 plates, with 9 windows in total.
The 9 windows have 45 panes, 7 of which are square and 2 are ball round.
36×1 + 7×4 + 2×8 = 36+28+16 = 80.
The answer is 80 songs.
Your result for task 6:
You have proven yourselves to be true puzzle masters.
Therefore I will give you the last letter to my secret word: C
Now go to the water and find a nice place to solve the last task.
Do not press “Next” before you are ready to solve the last task.
Everybody else can then press “Refresh”.