Is it dangerous to lose weight quickly? I weigh 253lbs and I'm 5'8 in height. I want to lose 73lbs before 7 months is passed. Should I cut out sugar?

Weight Loss. Reduction of sugar can definitely help. Calorie control with multiple small meals with a balanced diet and regular exercise that includes resistance and cardiovascular activity with help you loss a healthy 1-2 lbs a week. To loss more than this rapidly best to be involved with a physician supervised program.
Carbs. You can try to cut out sugar and carbohydrates. Or at least minimize your intake. 70lbs in 7 months is 1.25lbs a week. I can be done with diet and exercise. Check with your doctor to make sure everything is fine physically before you do strenuous exercises. Then good luck.
Weight loss. You can lose weight too fast, it's called starving or anorexia. You want to lose about 1-2 pounds per week. Cutting out sugar is good. Dietary change makes the biggest impact, just make sure you are getting adequate nutrition while you losing those pounds. Good luck.