Question

why the mango and all fruits are sweet​

Answer 1

Mangoes are juicy stone fruit (drupe) from numerous species of tropical trees belonging to the flowering plant genus Mangifera, cultivated mostly for their edible fruit.

The majority of these species are found in nature as wild mangoes. The genus belongs to the cashew family Anacardiaceae. Mangoes are native to South Asia,[1][2] from where the "common mango" or "Indian mango", Mangifera indica, has been distributed worldwide to become one of the most widely cultivated fruits in the tropics. Other Mangifera species (e.g. horse mango, Mangifera foetida) are grown on a more localized basis.

Answer 2

in general raw fruits contain more acid than ripen fruits but on ripening quantity of acid in then decreases and the level of sugar increases in the fruits. the degradation of starch by amalyse produces sugar