@MEENA JI I'm so glad you asked about Monty's diet. A macaw's diet (especially when young) is critical for their lifetime health.
A good pellet is the basis of any diet for these high energy, large birds. I don't know what pellets are available where you live, but here is a list that Mizzely has put together;
Pellets for Parrots
Harrison's, Roudybush and LaFeber's are generally considered the three best. The reasons are - No sugar - no dyes - and inclusion of vitamin D3, A, E and other trace vitamins and minerals. A bird can live exclusively on any of these pellets for their life time, but that's too boring for them . If they will eat any of them - if not you will have to find another pellet as close as possible to one of these.
In addition to a good pellet - available to them 24 hrs per day - a vegetable chop should be fed once per day. The list is long for acceptable vegetables. Carrots, romaine lettuce, beets - there are many great recipes for chop on this forum. Monty may have a preference of how he likes them presented - finely chopped, large pieces, whole vegetable - you will find out what he prefers.
Nuts are good for macaws as long as it is a good nut. NEVER FEED PEANUTS TO MONTY. Peanuts are ful of saturated fats and very dangerous for aspergillosis and aflatoxins - both deadly. My Jasper just died from Aspergillosis two weeks ago (she didn't contract it through peanuts) . Walnuts, almonds, pistachios, pine nuts are all good for them. Almonds are the best because they are high in calcium and the lowest in fat. Pine nuts are great for treats and training - small and quickly eaten.
Very little fruits. There is way too much sugar in fruits. Papaya, mango, apples, peaches - many are good, but papaya and mango are best. Give as treats or maybe a couple of times a week.
Keep in mind that macaws need a lot of protein (vegetable protein. not animal) and a higher amount of fat than most other parrots, but as much of the fats as possible should be unsaturated fats. I personally recommend Flax oil or Red Palm Oil as a lifetime supplement for your bird.
Ask any questions you have.