Hey @ppropanda34! Welcome to the forums!
Try following the link on “Düğüm: Set Weapon_Enum” to follow the error to the node and send us some pictures!
This is a very common error and simply has to do with accidental misuse of the Cast node.
What it is saying is you don’t have an appropriate reference for the cast.
Keep in mind, casting is NOT communication between actors. It is more like a mold, you mold what goes in to something more specific to access more specific features of the actor. 