How does bell's palsy progress?

Variable. The course of bell's palsy varies from person to person. It is thought to be due to a viral infection that causes swelling in the facial nerve and leads to weakness or paralysis of the facial muscles. This can occur over the course of hours or days. Fortunately, most people recover normal facial function but this can be permanent.
Depends. It can progress over hours or days. It's important to seek medical attention immediately to make sure there are no other medical issues causing symptoms.