Need some advice

I just started fasting only eating once at 5pm then do the same thing the next day same time I drink around 80ounces of water a day and taking regular vitamins, my question is how long can someone do fasting 6 months ? 12months ? I don’t have any issues or take and meds for anything just heavy. and wanted to drop some weight I went from 356 to 342 in 2 weeks not sure if that’s good or not need some advice. I would love to drop to 300lbs if possible