First, the physical aspect is to test your current physical function, such as measuring your fat content, your body circumference, your heart and lung function, reaction speed, body flexibility and so on. These data are very important. Exercise should give you personalized exercise according to these data. Because everyone's physical condition is different, it is impossible for everyone to train in the same way. With these data, you can tailor your training plan to ensure your own safety to the greatest extent and avoid injuries caused by sports. Of course, if you don't do this, experienced coaches can see your physical condition, and if you don't have a very formal fitness club, the measured data may not be very accurate. So you can buy cheap ones directly online and ask a personal trainer to save money.
Second, both treadmills and elliptical machines are aerobic exercises, and their functions are the same. If you are tired of the treadmill, change the elliptical machine and adjust it to give your body a new stimulus. The difference is that the elliptical machine may hurt your knee a little less.
Third, let me give you a suggestion. Your weight is already obese, but it is actually a disease. Losing weight is not as simple as exercising in life, but a method to treat obesity. So you should be professional and find a good undead coach to help you. Although the coach is expensive, it is really worth it. Because health is the capital of life.