I cant finish the skip even I watched the speedrun video many times

They can skip the animation when they first time meet Undyne in Genocide speedrun,but I can't understand how to do that with the phone

There is no more useful video than wr speedrun in Chinese website,so where can I find a detailed vedio or guide on Speedrun.com?

There's information in the text guide, which you can find here: https://oceanbagel.github.io/UTSRGuides/#/CategoryGuides/MainCategories/Genocide?id=sgs-spears-amp-glad-dummy