Normal antibiotics do not treat or get rid of the virus causing Pneumonia so your doctor will actually give you antiviral medication to get rid of the pneumonia.
When taking the antiviral medication for the Pneumonia you should be getting over the pneumonia within 1 or 2 weeks.
If the pneumonia lasts longer than a few weeks then you should see your doctor again or visit the emergency room because the pneumonia could be worse than you thought and could be deadly if not treated soon enough.