How to reduce weight?

my age is 25 and height is 165 cm..and weight is 60..it's been 3 months i'm going to gym but i did not reduce 1 Gram also..in my daily routine day start with breakfast one chapati..than lunch is 2 chapati,dal,subji(cooked vegetables),evening musli-milk n one banana..and i do 1-1.5 hrs of gyming..i'm frustated as why it is not reducing help me reduce 4-5 kgs weight..wht should i do???