I dont actually know why but I am trying to learn Pokemon Red by playing and watching a stream at the same time and no matter how fast I mash in the Intro I always fall behind at the Nidoran Cry... Always. Its like my Game frezzes at this Cry for half a second or something but after 80 trys its 100% the Case. What am I doing wrong here?

Hold B and Mash A.

Do I have to hold B and Mash A for every Textbox or is it enough to just spam A or B for the most?

During the intro and for every textbox until you set textspeed to fast