If you only have a short time to visit Provence but want to see as much as you can then this is the itinerary for you ! Your 4 days here will take you to Aix en Provence, Gorge du Verdon, the villages of Luberon and Marseille. This will give you an amazing taste of this breath taking region.
I'd recommend Aix en Provence the most as a base for the trip as it's the most centrally located here, but you can also stay in Marseille or Luberon.
For this itinerary you'll need a car or you can book tours to Luberon and the Gorge, which are both very rural.