How long untill i start seeing improvement for persistent sinus infection i already had endioscopic surgery and the infection came back?

Ask your surgeon: The purposes of sinus surgery can be summarized in two words. Ventilation and drainage. That does not mean that you can not develop an infection in those same sinuses following a viral infection of the nose. It is impossible to really answer your question because we do not know how extensive your sinusitis or surgery was. Did you have polyps. They often recur. Check with your surgeon.