What to eat? We don't do meal plans, per se, but I can give you some ideas. Stick with as many fresh veggies as you can, low/no fat dairy, lean protein, whole grains, good fats, nuts, seeds, etc.
Stop drinking sodas - drink water instead. Stay away from candy bars, cookies, anything with with white sugar and flour. Swap white rice, for brown, and regular pasta for whole grain. Opt for whole fruit instead of fruit juice. Limit portion sizes.
You should probably talk to your parents and get their support.
Exercise - walking is about as good as it gets and you don't need a gym membership to do it. Aim for at least 30 minutes/day.
You can google "exercise videos" and I'm sure there will be a lot of sites from which you can watch for free. You might also check out some yoga videos. Yoga is excellent exercise as it helps tone muscles, as well as build them.
By the way, 45 pounds and 60 pounds is too much weight loss in only 3.5 months. You might want to set your sites a bit lower. Safe weight loss is 1-2 pounds/week.
You might want to change your eating habits in stages. First, if you are on sodas, eliminate them. When you have adjusted to that, cut out candy and desserts. Then cut out junk food. You are almost there...
Now increase your intake of vegetable and fresh fruits. Once you are on a healthy diet, consisting of moderate portions, you will never have to think about your weight again.
You will not achieve your goal by your birthday, but you will be slimmer and more attractive by then and the change will be noticeable.