Visual studio doesn't recognize renamed namespace

Visual studio doesn't recognize renamed namespace

I changed a namespace and an assembly name and visual studio started to
complain that it can't find the class in the namespace. It still suggests
it here:
But when I try to run the project it says that: Here is that class:
And here is the renamed assembly and namespace
I'm about to hang myself, because I didn't backed up the project and don't
use any version control software and the whole day of searching for the
cause of it resulted in nothing. I didn't have the need to rename projects
before, so perhaps I'm missing something really obvious.