Chart value labels overlap, not readable

The attached chart demonstrates that the value labels may overlap, hence making at least the one in the back badly readable.

Notice how the 158 bpm label is very difficult to read, while the 30.1 km/h label readability is impacted, too.

Depending on the relative position of the back label to the front label, it could be shifted up (or down), to prevent the overlap. Once this shift has taken place, the grouping of _both_ labels need to be shifted down (or up), in case they went outside of the viewport (this avoids that the shifted label is cut off).