Symfony Server crashes when extending FOSUserBundle's default template layout.html.twig

I am trying to get the basic user login running from the FOSUserBundle. I am using Symfony 3.0.6.

I followed the description to setup everything from the FOSUserBundle: https://symfony.com/doc/master/bundles/FOSUserBundle/index.html

DB is up and running everything seems fine except I cant figure out how to override the layout.html.twig from the FOSUserBundle. I followed this description for achieving that: https://symfony.com/doc/master/bundles/FOSUserBundle/overriding_templates.html

I now have a file "layout.html.twig" in the folder "Resources/FOSUserBundle/views" with the content being the same as in the last link provided above. This leads to the following error:

Unable to find template "layout.html.twig" (looked into: [somePathInfo]) in FOSUserBundle::layout.html.twig at line 1.

Now I changed the first line in the "layout.html.twig" Template to be

{% extends 'FOSUserBundle::layout.html.twig' %}

And this then leads to the symfony server to crash stating

>php bin/console server:run -v [OK] Server running on http://127.0.0.1:8000 // Quit the server with CONTROL-C. RUN "C:xamppphpphp.exe" "-S" "127.0.0.1:8000" "[PATH]myProjectvendorsymfonysymfonysrcSymfonyBundleFrameworkBundleResourcesconfigrouter_dev.php" RES -1073741571 Command did not run successfully [ERROR] Built-in server terminated unexpectedly.

I am stuck here... Any ideas are very welcome.