I am a 15 year old male about 178cm tall (5 feet 10 inches) weighing 80kg. Before starting my diet I weigh 90kg and lost a total of 10kg in about 4 months. My diet is kept to about 1500 calories a day with little to no exercise. The problem now is that I am worried about my metabolism rate is decreasing from dieting. I recently looked up on the internet that your metabolism slows when dieting. The article I looked up mentions about our body adapting to the energy deficiency in our body and slowing down our metabolism rate. I am wondering if this is something permanent or if I can eat the regular amount it takes to maintain my weight once I reach my ideal weight.

It's unlikely to be permanent. Many factors influence the metabolic rate.

You're only 15 and your metabolism is supposed to be in boost.
Can you share that article?