Aiming to loose weight over time gradually will build a long term habit. Loosing weight fast will be harder and you'll probably put most of it back on.
To loose weight fast, eat 1200 calories a day, any less and you'll be malnutrioned and gain weight and fat. Do HIIT training for 30 minutes twice a week, on separate days do 30-45 minutes of resistance training twice a week, and finally go for atleast 3 brisk 30 minute walks a week. Do this for 4 weeks and you'll do well.