Do toenail go back to normal after a fungal nail infection?

If the shape is norm: Toenail fungus will deform the shape of a toenail if the infection is present for too long. If you catch it before the nail has changed shape, it will go back to its normal shape after treatment. If the shape has changed, it will look much better, the color and texture will be restored, but the shape may be permanently changed.

Sometimes: The nail is dystrophic or injured. Even if the fungus is gone the nail could remain abnormal.

Sometimes: It depends on the severity of the infection and type of treatment. Have your nails evaluated and get the appropriate treatment.

Yes but not always: If the fungus did not damage the nail root then once the fungal infection is cured the nail should grow back normally. If any damage to the nail root occurred then the nail because injured (dystrophic) and will grow back abnormally but without the fungus.