For the first one, draw a picture. You should see that the light pole, the line from the base of the light pole to the end of Johann's shadow, the line from the light to the end of Johann's shadow, and the light pole make a right triangle. Further, Johann himself is a vertical line inside that triangle and so forms another right triangle that is similar to the first. You can use the basic property of similar triangles, that ratios of lengths of corresponding sides are equal, to set up an equation that gives length of the shadow as a function of his distance from the shadow. Then differentiate both sides with respect to time to get an equation connecting their rates of change.
For the second, much the same thing except that now it is the vertical side of the right triangle you are given a rate of change for, rather than the horizontal side.