Hello Doctor, How Soon Can I See A Consistent Change

Hello Doctor, How soon can I see a consistent change in my High blood pressure if I change my diet, increase my potassium levels and take magnesium? My blood pressure was 180/90 on Tuesday. The next day on Wednesday, my pressure was at 139/78 in the morning, but around lunch time after eating it was at 150/98. Around 1:30pm, my pressure was down to 139/78 again. My issue is more genetics and age. I am 5'2", 108 lbs and workout 5-6 days per week. My eating habits were not horrible, but only required tweeking.