Hello Werner,
Thank you for the hint.
I guess they are more clear in the attached picture. (the indication numbers were in black color, not easy to see)
About the sum of two signals, is it correct to say:
The max of the sum corresponds to the coincidence of the signals maxima
The min of the sum corresponds to the coincidence of the signals minima
How about the coincidence of one max and one min? in that case the sum would be close to zero but it may also happen when two signals zeros coincide with each other.