How to prevent dizziness and fatigue?

Hey, I regularly fast for 12 hours, basically I do Intermittent fasting whole day. But recently I discovered that fasting for 3 days helps in autophagy, body cleaning itself. So I started to fast. At around 24 hour mark, I felt hunger so I drank water to supress that. Surprisingly it worked. Around 40 hour mark, I felt very hungry. I was tired, low on energy and dizziness was hitting me, so I broke the fast and ate a banana. Seeing here people fasting for weeks, days, 10 days, 20 days , 30 days. How do you even manage to be functional? Like ik body shifts to burning fat, but like how do you have electrolytes? Like any electrolyte powder, or maybe salt water work? Please help me out how to deal with problems you face when you fast for 50+ hours. Also how should I workout in the gym? Should I stop it? Because I take around 100 grams of protein each day. If i would fast, how should I manage this. Any help is really appreciated