After following all the steps and check and re-check my code I still have an error for which I can't fint the solution yet. Anyone having the same issue?

Slim Application Error

The application could not run because of the following error: Details Type: Slim\Exception\ContainerValueNotFoundException Message: Identifier "course" is not defined. File: /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/Container.php Line: 120 Trace

0 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/Container.php(172): Slim\Container->get('course')

1 /Users/Christian 1/php_rest_api/src/routes.php(11): Slim\Container->__get('course')

2 [internal function]: Closure->{closure}(Object(Slim\Http\Request), Object(Slim\Http\Response), Array)

3 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/Handlers/Strategies/RequestResponse.php(41): call_user_func(Object(Closure), Object(Slim\Http\Request), Object(Slim\Http\Response), Array)

4 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/Route.php(356): Slim\Handlers\Strategies\RequestResponse->__invoke(Object(Closure), Object(Slim\Http\Request), Object(Slim\Http\Response), Array)

5 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/MiddlewareAwareTrait.php(117): Slim\Route->__invoke(Object(Slim\Http\Request), Object(Slim\Http\Response))

6 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/Route.php(334): Slim\Route->callMiddlewareStack(Object(Slim\Http\Request), Object(Slim\Http\Response))

7 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/App.php(515): Slim\Route->run(Object(Slim\Http\Request), Object(Slim\Http\Response))

8 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/MiddlewareAwareTrait.php(117): Slim\App->__invoke(Object(Slim\Http\Request), Object(Slim\Http\Response))

9 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/App.php(405): Slim\App->callMiddlewareStack(Object(Slim\Http\Request), Object(Slim\Http\Response))

10 /Users/Christian 1/php_rest_api/vendor/slim/slim/Slim/App.php(313): Slim\App->process(Object(Slim\Http\Request), Object(Slim\Http\Response))

11 /Users/Christian 1/php_rest_api/public/index.php(33): Slim\App->run()

12 {main}