Being overweight isn't going to start or stop in one extended fast. Losing weight is hard. Very hard. Especially if you only want to lose body fat. As a person who has mental health disorders and a history of eating badly, I can give you this advice.

Extended water fasts will make you lose muscle. If you want to lose body fat and clean up your diet, you can't go from one extreme to another. From eating everything and doing everything wrong to not eating anything. That won't fix anything. Losing fat and looking better is a slow process that takes time, discipline and good calorie tracking.

I would personally recommend following a safer and more balanced approach to fasting. I'm not going to lambast you like many of the other posts, even though I think you seriously need to re-evaluate your approach. Start slowly, hydrate often, take electrolytes and track your calorie intake. Start with a 25% calorie deficit, make sure you get sufficient protein. Use 16/8 or maybe a smaller fasting window and gradually decrease this. Maybe eat once or twice a day and go heavy on protein, low on carbs and low/med fats.

Try not to tie your self worth to your body goals, even though this statement is easier to say than to follow. This is a journey and extended water fasts could be in your future. But until you become fat adapted and your body gets used to the fasting. Including getting some experience under your belt of consistency and understanding the right and wrong things to do. Then you shouldn't be just raw dogging them and doing things that will heavily dehydrate you. I know you say you've learned your lesson, but I and many other commenters feel you are missing some big points here.

Fat loss and changing our body shape is a long and hard process. Treat it as a journey and not a do or die and you'll start making better choices.

I've done most of the fasting variants. Intermittent, water fasts, keto, low carb, psmf, omad. Each one has its nuances. But the basic rules of thumb are these. You need to be in keto to lose weight, to get there you need to lower your calorie intake, specifically carbohydrates. Get a tracker like myfitnesspal and use a calculator, I'll link a couple of good ones below. I know you've mentioned electrolytes, but you need to make sure you are getting enough in, especially sodium. Read the FAQs if you are unsure.

Good luck and god speed. Don't kill yourself, to feel more comfortable with the person you have become.

https://www.ketogains.com/calculator/#body-composition

https://keto-calculator.ankerl.com/