Great job mate! Dry fasting isn’t easy and takes a lot of discipline. Don’t be discourage that you lost water weight because a good amount of it is also fat.
When you deplete your body of all the glycogen/water from your last meal in your liver/muscle, your body has to find other sources of water since you’re not consuming any. Where will it go? To your fat. Since you’re fat cells are made mostly of water (H molecules), it’ll break it up and turn it into water.
So, the first day, you’re losing most/all water weight depending on how much water you hold. After, you’re burning straight fat. Like I said, you definitely burn fat during your fast. Keep it up and don’t undervalue your accomplishment. You did great 👍!
Unfortunately you won´t maintain the weight loss, but sure some of it, would recommend doing a low carb diet option and intermittant fasting. Downside with low carb is that you will gain some of that back too when you start eating normal, but that´s pretty much just water tied to glucose.