Hello Everybody

i have Problems with my Custom Table and the DataObjectManager.
In my current Project is the case Locations. User can Submit a Location, all Locations are listed in a Table with a link to a detailed View.

Structure:
1. Locations (All Locations - listed in Menu)
1.1 Add a Location (Submit - Listed in Menu)
1.2 Location (Detailview - not listed in Menu)

As i read the Polltutorial i created a Submission.php where my Table is set up, now i think doing it that way is wrong and won't work with my DataObjectManager. I think some Relations are messed up or i have 1 File too much.
Anyway... after 2 hours of trying to understand some Tutorials in the Docs i am stuck now and looking for Help.

Here are my PHP Files a Screenshot of my .ss Folder and a Screenshot of the Error i receieve on the Page "Location" in the CMS which is the Detailview.

MySite/Location.php

<?php

	class Location extends Page {
	
		static $has_many = array(
			'Locations' => 'LocationSubmission'
		);
	

		function getCMSFields() {
		
			$fields = parent::getCMSFields();
			$fields->addFieldToTab("Root.Content.Locations", new DataObjectManager(
				$this,
				'Locations',
				'LocationSubmission',
				array('Name' => 'Name'),
				'getCMSFields_forPopup'
			));

			return $fields;
		
		}

		// Get Location by ID (Detailview)
		function GetLocations()
		{
			return DataObject::get('Location', 'ParentID = {$this->ID}', 'ID DESC');
		}
	}


	
	class Location_Controller extends Page_Controller {
	
		public function GetLocationSubmission(){
			$Params = Director::urlParams(); //This gets our URLparams
			$SubmissionID = $Params['Action']; //gets the ID from our $Params array
			return DataObject::get_by_id("LocationSubmission", "$SubmissionID");
		}

		function ContactForm() {
		  // Create fields
		  $fields = new FieldSet(
		     new TextField('Dein Name'),
		     new TextareaField('Deine Nachricht')
		  );
		  
		  	// Create actions
		$actions = new FieldSet(
		 new FormAction('ContactForm', 'Absenden')
		);
		
		// Create validator
		$validator = new RequiredFields('Name', 'Deine Nachricht');
		
		return new Form($this, 'ContactForm', $fields, $actions, $validator);
		  
	}
		
			
	}


?>

<?php

	class LocationAdd extends Page {
	
	}
	
	
	class LocationAdd_Controller extends Page_Controller {
	
		// Start Form
		function Form() {
		
			// Fields of Location
			$fields = new FieldSet(
				new TextField('Name','Name der Location'),
				new TextField('Author','Name des Ansprechpartners'),
				new EmailField('Email','E-Mail  des Ansprechpartners'),
				new TextareaField('Description','Beschreibe deine Location'),
				new TextField('Adress','Adresse'),
				new TextField('PLZ','PLZ'),
				new TextField('Location','Ort'),

				new DropdownField('Country','Land',array(
				#'' => '',
				  'Deutschland' => 'Deutschland',
				  'Schweiz' => 'Schweiz'
				  )
				),
				
				new CheckboxSetField('Table','Kickertisch(e)',array(
					'Lehmacher'=>'Lehmacher',
					'Tecball'=>'Tecball'
				)) 	
						
			);
			
			$actions = new Fieldset(
				new FormAction('addLocation','Eintragen')
			);
			
			$validator = new RequiredFields(
				'Name',
				'Email',
				'Description'
			);
			
			$form = new Form(
				$this,
				'Form',
				$fields,
				$actions,
				$validator
			
			);
			return $form;
			
		}
		// end Form
	
	
		// Dateneintrag
		function addLocation($data,$form) {
			$location = new LocationSubmission();
			$form->saveInto($location);
			
			$location->write();
		
			$form->sessionMessage(
				'Eingetragen - wird geprŸft',
				'good'
			);
			Director::redirectBack();
			return;
			
		}
	
	
	}
	// end Class

?>

<?php
	class LocationSubmission extends DataObject {
		static $db = array(
			'Name' => 'Varchar(200)',
			'Author' => 'Varchar(100)',
			'Email' => 'Varchar (100)',
			'Description' => 'Text',
			'Adress' => 'Varchar(150)',  
			'PLZ' => 'Int(5)',   
			'Location' => 'Varchar(50)',
			'Country' => 'Varchar(50)',
			'Table' => 'Varchar(150)'   
   
		);
		
		static $has_one = array(
			'LocationSubmission' => 'LocationSubmission'
		);
		
		public function getCMSFields_forPopup()
		{
			return new FieldSet(
				new TextField('Name')

			);
		}
		

	}

	
?>

<?php
	class LocationHolder extends Page {
		
		static $allowed_children = array(
			'Location'
		);
		
		function LocationShow ()
		{
			$sort = 'Created DESC';
			
			$data = DataObject::get('LocationSubmission','',$sort,'','');
			return $data;
		}
	

	}
	
	class LocationHolder_Controller extends Page_Controller  {
	

	
	}
	


?>

This kind of Case will come one more time in that Project and a few times in Future, so now i want to make sure i am doing the right way and looking for help here.

PLease show me what i am doing wrong.

Thank you all!