IsTouchingLayers

I'm trying to create a 3D endless runner/ sidescroller platform game. I'm trying to detect when the player is touching the ground and every time that is touching it i can click and jump as many times without any problem. But at the moment I facing the problem that is jumping to high everytime that i input the key code. I try to fix this with layer mask but the isTouching Layer is only for physics2D. Any suggetion of what to do???? This is the code that I currently have