You have high myopia but on the low end. Most definitions make high myopia greater than 6 diopters of myopia. Most high myopes don't develop myopic mac degen There is no way at your age to "stop myopia" You should lead a healthy life, don't smoke or use cannabis, exercise moderately, watch your weight, have annual physical and eye exams and discuss further with your ophthalmologist.
my first glasses were -1.00 both left and right