Loose fat from stomach. Fat sooner!

I gained weight in 3 months from 43 Kg to 58Kg due to having cheese sandwich or burger with fruit juice containing sugar as breakfast, curry chapati(or puri) and fruit juice as lunch and dinner too, mayonnaise sandwich as evening supper and also I most of the time have fruit chat as lunch. I want to get flat belly so from almost 3-4 months I left having mayonnaise or cheese, I left chocolates, rarely I eat pizza, burger also for initial 2 months I started going to gym but later I couldn't continue because of work. Now from almost 3 months I take green tea with lemon and honey in morning with empty stomach and mostly eat homely food but it seems like nothing is happening and even more fat is accumulating . I've done thyroid test but it was negative. Can you suggest me some effective remedy to loose belly fat sooner