smooth transition in blend tree for walking animation on unity

I created walking animations with an animator in Unity using a blend tree. The animation is based on two parameters (horizontal and vertical axis).

Unity Parameter IsRunning does not exist. Unity.Engine.Animator:SetBool (string,bool)

I try to make a survival Game like in this Tutorial here: https://youtu.be/_GzSfnJNNI4?si=UasH0Eb8Fc1zzP3a