What causes primary hypertension why does blood pressure in people with hypertension starts to rise suddenly can hypertension be cured?

There is no specific "cause" of hypertension. Genetics play a role as do lifestyle factors like salt intake, diet, obesity. If one is overweight and consumes lots of salt, dietary changes and weight loss, exercise can eliminate hypertension but one would have to follow that lifestyle for life. If one does not change lifestyle habits(and even in some with changes) usually you are on medication .