I've heard from many people that if you are exercising at the gym, then your height will stop increasing. Is it true for 19 year old male?
The exercise itself will not impair your growth. In fact, exercise can increase secretion of Human Growth Hormone, which can lead to a height gain. However, if you are chronically under-nourished, there is a risk of you winding up a few inches shorter than you might have been. If you injure your growth plates, that may affect bone growth, but the risk is primarily in broken bones, and even those seldom cause problems if properly set.
It is true that lifting weights will temporarily make you shorter due to compression of the spine, but the effect is entirely temporary.
It depends. If you do plenty of cardio (e.g. short burst sprinting, swimming, etc.), your body will secrete growth hormones.
However if you lift heavy, especially chest or back related workouts since your bones are less dense and still growing it will stunt that growth.
I suggest doing more high intensity workouts with lower weight and higher rep range!