Hoffman degradation is the reaction of primary amide with halogen in presence of strong base to give amine.

In first step the base abstract the proton from amide and form amide anion.

This amide anion attack on the halogen to form the n- halo amide which on rearrangement gives the ketene intermediate.

The ketene intermediate further react to give amine.

Though it is difficult to explain the mechanism without the representation of reactions diagrammatically,hope you understood the mechanism.