Eat between 1300-1700 calories a day (roughly), don’t go lower because it isn’t good for you, especially in the long run!
Healthy eating and exercise is the only way I will recommend you to lose weight.
Possibly because you tend to lose a big number when you start eating healthy from not eating healthy so it’s not impossible. However with you being at such a small weight to begin with I’d say it wasn’t very likely.
Good luck though! Please don’t harm your body with under feeding it.