Since you are overweight with hypertension, you must avoid heavy workout in a gym as it can be dangerous. First get a fitness evaluation done by a physician to ensure you are medically fit for gym exercises. Otherwise, it will be better to lose weight by brisk walking which is natural and safe and can be continued lifelong. Focus on changing your eating habits and lifestyle more than weight loss. When you make changes in your diet and increase physical activity, you will not only lose weight gradually, but will also be able to control your blood pressure and improve overall physical fitness. Hope this will help.