This seems pretty simple… I have the floor Bp with a custom even to turn invisiable…then I have an opject that when you get into the trigger box you should be able to hit “F” thereby by triggering the Custom event…
I have (In the floor BP) The floor referenced and in the Custom event trigger, I have the Floor BP referenced…
You sure you set New Var 0? Object varable is empty by default, you need to set it first in order to call function on them. If you place those actors on level, press eye icon in New Var 0 and in level in details tab set the object.
No, you only set type of varable, object of a class Floor Bp, but it’s empty, you need to get object and set it to varable, staticly you can only set it when object are on the level, otherwise you need to get it dynamicly, most simple but kind of expensive way is use “Get All Actors of Class” niode
Could you please show me what you mean by
“Get object” I am a Noob and in need of help. 
Get object by other nodes that exist to get object, there many of them for diffrent perpaces i’m not sure which one will be best for you. If your objects are on the level then as i said set varble in details. If you spawning in some blueprint keep object that it’s returning in varable, Spawn Actor returns object that it’s spawned. Most universal way of getting object is using “Get All Actors of Class” where returns array of all objects of specific class, but this is kind of heavy weapon as i said. Additionally most classes have functions which let you access related objects for example from Pawn you can use Get Controller, which will return you controller that currently possesses the pawn.
This is really basics of basics, check my tutorial about objects and classes
