Could a bird suit make you able to fly if it were made of real feathers?

NO ... While feathers do play a major part in the flit of aviators it is the hollowest of the bones that allows birds to take flit ... However a person may be able to glide in a bird suit ...

In the early 1900's people actually tried this idea ( there is film of it), but as the answer above states birds have hollow bones ( we do not) and gravity prevents this from working. So, the answer is no.