My baby has 5 month old, and he needs a surgery because his hidronefrosis (5 level) and poor kidney funtionality. Does he need to wait to do surgery?

Probably. In adults, hydronephrosis (swelling of the kidney due to obstruction of urinary outlet) in the setting of poor kidney function should get treated sooner rather than later in order to have the best chance at preserving kidney function. In children, with both hydronephrosis and ongoing kidney injury, surgical management becomes more urgent.