To the first question, make your expression labels in the chart properties, Expressions tab, have the expression for the percentage. As a very basic example, the following should go in the expression label:
='Sales % is ' & Num(Sum(Sales) / Sum(TOTAL Sales), '#.##0,00%')
To the second, it depends on how you are creating your chart. Can you upload an example with dummy data on what you already have and what do you expect?
Hope that helps.