Is it true that carbohydrates have sugar ? if it is then how much do we need to consume it ?

Many carbs don't: All sugars are carbohydrates but most carbs are not sugar. We don't need to consume any sugar, but low-sugar carbs should be our main source of calories. It is healthy to eat fruits that do have some sugars, but no one needs refined sugar. For a good discussion of the difference between "good" & "bad" carbs see http://www.Hsph.Harvard.Edu/nutritionsource/carbohydrates-full-story/.