GSD bit me !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!…

i'm 14 and i have a czech working line german shepherd, and it's been introduced to pressure on the bitesleeve training done by the breeder i got him off. and today he tried to full on attack me man, it was not a lil snap it was a full on lash out chasing me so i punched him, dragged him on the floor until he calmed down. he's now gone proper submissive on me but like wtf??? why did he attack me