How to make a diet? And how to dont stop it?

You are the answer. You'll need to plan. If you are looking to lose weight, have a calorie goal i.e. 2000 calories per day. A good free app that helps keep track of this is myfitnesspal. Eat 3 meals per day with 1 small snack at 10am and 3pm. Eat your meals at the same time every data. As far as sticking to your diet, only you can answer that. You will have to make the decision to reach your dietary goals. Good luck!