Senior citizen

I am 67 years old, 30 lbs overweight and out of shape. I have cut out sugar, eating low carb and walking 3 Miles 4-5 times a week. I have lost my core! I’m looking for a starter program so that I don’t get discouraged and am not so sore that I can’t walk. I broke both ankles summer 2017 and have significant metal in one. Step classes aggravate my ankles. Oh, I also have COPD.