The car won't start and has oil leaking tonight oo]wPODdDDd

Hi everyone, it's been a few days now that my car has been having a problem: when reducing the speed to either stop in a traffic light, at a stop or anywhere else, the vehicle stalls. Revolutions reach 300 per second and it stalls. This does not happen all the times, there are cases in which revolutions go high until reaching 900 per second and it stabilizes. Does anyone know which the cause might be? Both the filters and spark plugs of the car are new.