Go on YouTube and search for “filinov fast” and watch a few of them. The protocol for weight loss is 2 24 hour dry fasts per week while walking 10 kilometers per day. No need to jump into these super intense 7 day fasts right away.
Get some experience with shorter fasts. Do the walking or equivalent exercise like body weight work. Basic idea is to use up all glycogen without stressing too much.
Try this for a month or two. I think jumping straight into long fasts with exercise is a bad idea. Just try it.