Why does the rate of a reaction keep decreasing as the reaction advances?

Why does the rate of any reaction generally decrease during the course of the reaction?

Why does the rate of any reaction generally decrease during the course of the reaction?

Why does the rate of any reaction generally decreases during the course of the reaction?

Why does the rate of any reaction generally decreases during the course of the reaction?

If pH and temperature are kept constant, does the rate of reaction keep increasing with increase in substrate concentration?

Why does the rate of a reaction increase with rise in temperature?