For 2, just look at the map, find the river and estimate the area of the basin. For 5, look at the flood graph, divide it into 30 year chunks and read the height of the tallest bar in each chunk. Average that, and that's the 30 year flood.
As for the diagram in A, I'm guessing a little here but I believe the location of the letters represents a map view of their geographical position. The number is the hydraulic head, and the lines are isolines for hydraulic head. The arrow indicates the hydraulic gradient.
but for number two when i do that i get much larger numbers than 80 and 60 km