I've done two stone in 9 months, one to go.
Exercise is nonsense for weight loss, extremely unrewarding it takes about an hour to work off the calories from a bag of crisps that only takes 1 second of strength to decide not to eat.
Use a calorie app that also tracks weight and weigh yourself once a week on the same day, at the same time, morning and evening shifts in water and hydration can make a big difference and can be quite demotivating.
Aim for weight loss over a year or longer , that way you will have established actual behavioural change and not rebound once you hit your target.
I used nutricheck on my android phone which costs a small fee but calculates your required calorie deficit for weight loss in a specified time.
The thing that shocked me was portion sizes, especially things like rice and cereal, the other thing I noticed was enjoying food more once a pattern was established.