Solid enemy help

Hey i need help with my enemies. They keep walking into eachother, what i mean by that is they will walk through eachother and after some time has passed they combine forming one enemy but all of them are still there. Also they go through the walls and they go through the floor when trying to attack the player. I dont know where to start or to do anything anyone have any ideas plz help.

Apply a CharacterController or RigidBody(no gravity) + Collider (makes collisions happen among your enemies) and write an AI script to control movement behavior. Your walls and floors you will have to either create the colliders in a modeling program and import them in manually, or make your own box colliders around the objects in the Unity Editor. This will walk you through the procedure. Doesn't matter if it's 2D or 3D.