Hey doc I broke my ulna and radius in my left bone. And the doc put me a cast and I have too keep it and I want to know the chances if a surgery.

No need. majority of simple fractured will be healed with cast,specially if they are not displaced if the fractured badly displaced,and could not be set under anesthesia properly then open reduction and internal fixation will be needed,but you still end up in a cast anyway,so surgery does not replace cast,it is only for difficult fracture,