I am 5ft 9 inch but only 50 kg having a diet also ! What 2 do?:confused:

Are you asking how to gain weight? Your question sounds a bit tricky. Is that what you are asking. If so add it and myself or some one will be able to help you. We need more clarification before answering your question.

At 5 ft 9, your roughly 110 pounds, right, well that's abit underweight, of course depending on your frame, and sex, age, roughly you should be at least over 130 pounds.
But like what's been mentioned, we need to know what you'd like to accomplish. With the information I've asked for, we can get a better idea how to help.

Boost up your protein. That way you won't gain the bad kind of fat and hurt your body. I am assuming you probably can't eat too much in one sitting so try things like protein shakes in the morning.

Try Omega 3 fatty acids sources like tuna, salmon, flax, walnuts. Lean meats, skinless pountry, nuts, seeds, legumes, chickpeas, kidney beans, peanut butter, omelets, whole grain cereals, rice and pasta, granola, bagels and cornbread. With veggies, try avacodos, olives,potatoes, peas, corn, squash. And fruits, canned fruit with syrup, dried fruits, and fruit nectars. Healthy carbs like fruits, veggies,whole grains, olive oil, honey, jam, soy protein powder. Try protein powders, and nutritional supplements like ensure and instant breakfast cereal mixes with whole milk with each meal. You'll need at least 3 large meals and 3 large snacks, trying to add 300-500 calories to your normal intake. Just don't eat junk food, too high in transfat, and saturated fats.