How to auto buy during dips and sell at ATH?

Hey,

When I have a coin that I believe is going to go up steadily, but I also believe it will dip while I am asleep, I want to buy during that dip. Likewise, if it reaches a price that I believe will lead to a dip, I want to sell at that price. How is this done? I read about stop/limits where you can sell if it drops