Welcome to EmpowHER and thank you for reaching out to us for tips oh how to decrease your height. There is no way. Please don't believe any one who tells you otherwise.
Height is part genetics and part environmental. How tall or short a person becomes is estimated to be 80 percent genetic, with nutrition and other environmental factors accounting for the rest.
At age 17, you may be approaching the end of your growth spurt and might have reached your maximum height. Your pediatrician can determine this. The fact of the matter is if both of your parents are tall, you are going to be tall.
Care to share a few inches:)