I'm 15-180-80 What should i do?

So as i stated, my age is 15, my height is 180 cm, and my weight is 80 kilograms. I started gym 1 week ago and i dont know about my diet i want to lose fat & build muscle. Sooo should i do calorie deficit or bulk or lean bulk i really dont know what these terms are called maybe diets? idk i just want advice