Doctor told me that symptoms of pleural effusion wont go away in X RAY even after treatment is it possible?

It depends. So pleural effusion is seen on a chest x. ray, and after treatment (ie drainage), there should be a difference, however, if a cxr is taken day/ month later the effusion may have recurred. I do not have enough room to go into any further details however if a pleural effusion is seen on a chest x ray and it is large enough that it can be tapped, then it should be tapped for diagnosis & treatment.