Hello!
Plan your diet perfectly, go to a dietician and design a diet chart and start workouts initially with the help of a trainer. Cross training is fine and also wear proper shoes and rehydrate yourself and have healthy breakfast before exercising.
Start slowly and as you adopt increase the intensity and you can add some amount of weight training gradually.
Your input and output should be controlled properly to lose weight. Do not starve, eat healthy and avoid all junk food, fast foods, chocolates, sweets, deep fries, fat food etc.
Heart rate will stabilize and I also suggest you to get your blood pressure and pulse rate checked by a Physician both in basal condition and after exercise.
Take care!