Why charge reducing so fast?

Se reduce muy rapidamente la bateria, porque ha llegado al final de su vida util y ya no acumula carga. el siguiente paso si no la cambias pronto , es que la bateria se incha deformando la carcasa del telefono.

traducctor google

The battery is depleted very quickly, because it has reached the end of its useful life and no longer accumulates a charge. The next step if you don't change it soon, is that the battery swells, deforming the phone case.

There could be multiple issues. Firstly, you may have too much running at once. This would be solved by closing apps down.

Secondly, make use of the power saving function.

Finally consider replacing the battery