Hello everybody,
I am trying to install custom Block Types on my website. But as soon as a click on "Block Types" a "ReflectionException (-1) Class does not exist" shows up on my screen. Everything esle works propperly, it's just the Block Types.

The shown code is:
[ */
public function build($concrete, array $parameters = [])
{
// If the concrete type is actually a Closure, we will just execute it and
// hand back the results of the functions, which allows functions to be
// used as resolvers for more fine-tuned resolution of these objects.
if ($concrete instanceof Closure) {
return $concrete($this, $parameters);
}

$reflector = new ReflectionClass($concrete);

// If the type is not instantiable, the developer is attempting to resolve
// an abstract type such as an Interface of Abstract Class and there is
// no binding registered for the abstractions so we need to bail out.
if (! $reflector->isInstantiable()) {
if (! empty($this->buildStack)) {
$previous = implode(', ', $this->buildStack);

$message = "Target [$concrete] is not instantiable while building [$previous].";
} else {
$message = "Target [$concrete] is not instantiable.";
}

throw new BindingResolutionException($message);
}

$this->buildStack[] = $concrete;

$constructor = $reflector->getConstructor();

]

I allready reinstalled concrete5 and made a new Database.

Thanks for your Help
Alex