As a big girl {and I mean big big} I hesitate to reply to this however I did lose 40 lbs one year in an effort to help my back pain. At the time I was on reddit and I remember a gal who was sad she only lost 60 lbs in a year of her weight loss journey. I replied that she should be proud she had done a slow sustainable healthy weight loss rate and should be proud of herself so here it goes-- my advice:
meal plan and prep. Having preplanned breakfasts, lunches, snacks and dinners that you enjoy and that stay within your calorie target helps prevent being starving and eating high calorie for low nutrition pay off foods
find an exercise you enjoy. I agree with @shellygirl that weight training is the best because as you lose weight you will lose muscle mass unless you exercise and muscles burn more calories than fat does--plus muscles are best for reshaping your body even if you are overweight. I do not weight train myself tho I enjoyed it when I was younger. My personal easy to fit into daily exercise when I lost 40 lbs was walking... I did not need to go to gym, could do it at any time, didn't need a membership to anything etc etc. For a while I did go to a gym for weight training and walked to and from to get in my steps. I will add this was an excuse. You can do body weight workouts such as pushups and lunges that will help build some muscles without needing a membership to a club or expensive/fancy equipment.
Take it slowly. I realize we look in the mirror and self hate on our bodies and want immediate changes. It is healthier to lose weight at a rate of 1/2-2 lbs per week depending upon how overweight you are. If you are only needing to lose 20 lbs {and by need I mean
statistically overweight not just thinking you are fat because you are a size 10 instead of 2} then 1/2 lb a week is good. If you are
statistically obese aiming for 2 lbs a week is okay. I take this from reading such oldie but goodie books like volumetrics which recommend losing 10% of your weight over 6 months then maintaining the weight loss for next 6 months. So if you weigh 200 lbs you would lose 20 lbs over 6 months or @3 lbs per month aka 3/4 lb per week. If you are obese the author does state a rate of 20% of your weight over 6 months is okay. Several books recommend slow and steady for winning the weight loss game.
Personally I would rather lose 4 lbs a month over 12 months than 10 in a week and gain it all back as soon as I pick up a piece of toast.
Be kind to yourself. You will eat something not on your plan. You will go for periods of not losing weight {plateau}. Just stick to your plan. You may need to adjust how quickly you are losing as you lose that is to say that 1500-1800 calories per day {standard diet calorie goals} will cause a slower weight loss the less you weigh so increasing exercise or decreasing calories will help. I caution you not to drop below a certain calorie intake as your body needs certain nutrients that are difficult to get if you are too low in calories. You will lose muscle mass if you go too low and that will only bit you in the ass.
Also if you go too low your body will cling to your fat thinking it is starvation mode. My daughter dieted after her babies and had to up her calories from 1200-1500 to lose weight. I know that sounds backwards but at 1200 she was starving herself and her body resisted losing weight. Your physician can easily give you a calorie target as can several websites that talk about how many calories to lose weight slowly.
Be realistic about how overweight you are I particularly like
https://halls.md/ideal-weight/body.htm because it deep dives into how people your age and your weight would feel is ideal. Its a very interesting site for setting a realistic weight goal. There are also many articles on the site about healthy weight loss rates, BMI etc.
https://halls.md/weight-loss-percentage-calculator/
Love yourself. You are beautiful at 120 as you are at 300. Treat your body with respect. Feed it healthy foods {and your body does need carbs and fats and proteins they are macronutrients for a reason} and exercise and give yourself plenty of rest and try to keep yourself stress free {I use meditation and or breathing exercises}.