My weight is 54 kg and I want lose 4kg to be 50kg I eat a healthy food but I didn't lose any weight so what can I do and what diet I should follow?

Weight control. I understand your concern. “It is NOT what you eat It IS what is eating you!” At age 20 stressors of relationships, work, and unresolved conflicts can cause Anxiety and depression affecting motivation for exercise Accept yourself. Improve your self-esteem Exercise on a regular basis See a Therapist for coping with stressors, and to improve self image.
Diet. Increase exercise daily. 1200 calorie high protein low carbohydrate diet may help. Lab work for you is unknown and may need checked as well possibly medications may help. 64 oz of water a day and try to sleep 7 hours a night for starters.