It's good that you researched before wanting to do this.
You have to be very very VERY careful when fasting. You cannot workout or anything because that can be fatal to your heart!!! So please, no exercising. Get plenty of sleep!! Drink water like there's no tomorrow(obviously don't drowned your body)
To keep the weight off after breaking a fast, you need to for one, eat ONE piece of fruit first. An apple is a great choice. You don't even need to consume the whole thing. You have to literally eat super healthy after or you will gain the weight back and more.
You will gain water weight so don't be afraid of that. Nothing bad. Don't focus on the scale.
After you have that one piece of fruit, in three hours, have a veggie. Like a couple carrots, or a celery stalk, etc. three more hours later, make some juice. Make a healthy juice from whole fruits and veggies. You can search those up online for recipes!
Each day just keep adding more and more foods when you eat. Keep it steady!
OH AND JUST EAT EVERY THREE HOURS UNTIL YOUR BODY IS USED TO RHE FOOD. It gonna take a few weeks.
On your first day of breaking the fast, after you've ate what I've put down, the next day add in one more fruit or veggie.
Keeping adding foods. Depending on how healthy you wanna eat afterwards, add in whatever else but keep it small portions until your body can adjust to each food.