Interesting street photo work!...I loved photo #1 especially, as that dog's expression is frankly wonderful, plus the textures around it served as an eloquent framing.... Regarding that blur in the central part of the photos, I think it may be due to some dirt or fungus on the lens. I recommend that you take it apart and look at it against the light in detail, I'm sure there's something there causing that... The other black spots you mention, may be due to dirt on the camera sensor and when this happens they are more noticeable the more the lens diaphragm is closed. From the maximum aperture up to around f/6 they are not usually noticeable, but from then on they can appear as you close the aperture more... What you do in those cases is to clean the sensor carefully, I recommend to look for advice or a good instructive on the internet about how to do it in your specific camera model...

!PIZZA