im trying to learn the speedrun of grace but i cant get the speed strat where you wall jump and gain a lot of speed pls help me

in nmg 1.3 there is a new strat where you need to press "f11" but it makes my screen black for longer than the game reloads so i have to play without my screen for 1sec how can i fix that ?

(and why does my res always go to 1600x900 in the settings of poppy playtime)