If you asked magicians what the most important card sleights to have in their arsenal are, the list would vary. But in all of these lists one that would never be left out. And that would be the double lift.
The double lift dates back to 1776, but many magicians give credit to the late great Dai Vernon and his double turnover.
There are many versions of the double lift, but they all essentially perform the same sleight. That is, turning over two cards as one.
Some versions of the common routine, The Ambitious Card, rely heavily on the double lift, some even exclusively.
If you are looking to learn the double lift, I suggest getting a book such as Expert Card Technique by Jean Hugard, instead of learning it from some novice on YouTube.
Learning the correct way to perform the sleight will prevent yourself from picking up any bad habits.