Anything that relaxes you and reduces stress, such as deep breathing, can lower your blood pressure temporarily. However, these practices aren’t a solution for people with sustained hypertension. To manage your high blood pressure long term, you will need to make lifestyle changes (i.e. exercising, eating a healthy diet, limiting alcohol, losing excess weight, quitting smoking) and take medication as needed.
Reference:
Harvard: https://www.health.harvard.edu/heart-health/can-deep-slow-breathing-lower-blood-pressure
Cleveland Clinic: https://health.clevelandclinic.org/6-natural-ways-to-lower-blood-pressure/