oh you mean NPC boosting. There are 2 ways to do it:
unbuffered: just position yourself in the position you see in the video and then jump and instantly finish the dialogue. this is frame perfect so it is really hard.
example: runner: jjen.
pause buffered: firstly you need to bind the pause key to E. then you position yourself in the same area and then you press the E button and the space button at the same time. then you press E twice fast to unpause and pause the game again (this step is useful for positioning yourself in the right spot). then you need to finish the dialogue instantly using keyboard swapping. this method is easier but still really hard.
example:
also keep in mind you won't get the exact boosts as the video every time, the height of the boost depends on some factors but as long as you go high enough to bypass the wall that is blocking the access to the final level you should be good.
if you have any questions you can join the discord server or ask here