Problems with c++ variables in blueprints

No I didn’t set it, cause I didn’t know I have to do it. With an Object reference I can’t do it tho, it shows me “Editing this value in a Class Default Object not allowed” any idea how to fix this?

I’m using a classreference, cause I read it somewhere, that I might have to cast to the class, so I thaught I give a class reference a try.

edit: I found a work around. I just called get actor from calls and using that as variable. It works just as intendet. Thank you ver much for your help. So the missing refference was really the problem