A 30% loss of range isn't that unexpected with an EV during cold weather.
As for how long your battery will take to return to normal. That might take several days, the battery has a lot of mass and thermal inertia. Once it warms up it will behave as before.
As for how long your battery will take to return to normal. That might take several days, the battery has a lot of mass and thermal inertia. Once it warms up it will behave as before.