Confusion about comparing the charge densities of benzene and fluorobenzene
This is the way of directing the electrophiles to the ortho and para places  of the benzene cycle. As you see the ortho and para places are more negatively charged.That's true. It is due to the ability to donate its electron pair to the benzene cycle.

But an electronegative element can attract the electron cloud to it. Fluorine is the most electonegative element, so it has a greater ability to attract the electron cloud of the benzene cycle. So that makes it relatively  resistant to an incoming electrophile.

This does not say that it is not a  ortho-para director. It's a ortho-para director but it deactivates the ortho and para places of the benzene cycle.