add.ctp

<div class="box box-primary">
				<div class="box-header with-border">
					<h3 class="box-title">Neuen Artikel anlegen</h3>
				</div>
				<!-- /.box-header -->
				<!-- form start -->
				<?= $this->Form->create($article, ['class' => 'form-horizontal', 'type' => 'file']) ?>
				<?php 
					$myTemplates = [
					    'inputContainer' => '{{content}}',
					];
					$this->Form->templates($myTemplates);
				?>
				
					<div class="box-body">
					
						<div class="form-group">
							<label for="title" class="col-sm-2 control-label">Titel</label>
							<div class="col-sm-10">
								<input type="text" name="title" required="required" maxlength="255" id="title" class="form-control">
							</div>
						</div>
						
						<div class="form-group">
							<label for="text" class="col-sm-2 control-label">Text</label>
							<div class="col-sm-10">
								<textarea name="text" required="required" id="text" class="form-control textarea" rows="3" placeholder="Dein Text ..."></textarea>
							</div>
						</div>
						
						<div class="form-group">
							<label for="fachbereiche-id" class="col-sm-2 control-label">Fachbereich</label>
							<?= $this->Form->input('fachbereiche_id', ['options' => $fachbereiches, 'label' => false]); ?>
						</div>
						
						<div class="form-group">
							<label for="attachments-filename" class="col-sm-2 control-label">Datei</label>
							<div class="col-sm-10">
								<?= $this->Form->input('filename', ['type' => 'file', 'label' => false, 'multiple' => true, 'name' => 'filename[]']); ?>
							</div>
						</div>
						
					</div>
					<!-- /.box-body -->
					
					<div class="box-footer">
						<?= $this->Form->button(__('Speichern'), ['class' => 'btn btn-info pull-right']) ?>
					</div>
				<!-- /.box-footer -->
				<?= $this->Form->end() ?>
			</div>

ArticlesController

/**
     * Add method
     *
     * @return \Cake\Network\Response|void Redirects on successful add, renders view otherwise.
     */
    public function add()
    {
        $article = $this->Articles->newEntity();
        if ($this->request->is('post')) {
            $article = $this->Articles->patchEntity($article, $this->request->data);
            $saving = $this->Articles->save($article);
            if ($saving) {
                
                // Load Model to save attachments
                $this->loadModel('Attachments');

                foreach ($saving['filename'] as $value) {
                
                	$attachmentdata = [
	                	'filename' => $value['name'],
	                	'filetype' => $value['type'],
	                	'articles_id' => $saving->id
                	];
                	                	
                	$attachment = $this->Attachments->newEntity();
                	$attachment = $this->Attachments->patchEntity($attachment, $attachmentdata);
                	
                	$saveattachment = $this->Attachments->save($attachment); 
                }     
                
                // If saving article was successfull
                $this->Flash->success(__('The article has been saved.'));
                return $this->redirect(['action' => 'index']); 	
            } else {
                $this->Flash->error(__('The article could not be saved. Please, try again.'));
            }
        }
        $fachbereiches = $this->Articles->Fachbereiches->find('list', ['limit' => 200]);
        $this->set(compact('article', 'fachbereiches'));
        $this->set('_serialize', ['article']);
    }

ArticlesTable

public function initialize(array $config)
    {
        parent::initialize($config);

        $this->table('articles');
        $this->displayField('title');
        $this->primaryKey('id');

        $this->addBehavior('Timestamp');

        $this->belongsTo('Fachbereiches', [
            'foreignKey' => 'fachbereiche_id',
            'joinType' => 'INNER'
        ]);
        
        $this->hasMany('Attachments', [
        	'foreignKey' => 'articles_id',
        	'dependent' => true,
        ]);
        
        $this->addBehavior('Josegonzalez/Upload.Upload', [
        	// Configure as many upload fields as possible where the pattern is 'field' => 'config'
        	'filename' => [
        		'fields' => [
        			'type' => 'filetype' // Field to save filetype
        		],
        		'filesystem' => [
        			'root' => $_SERVER['HOME']
        		],
        		'path' => '{DS}Sites{DS}turngau{DS}webroot{DS}files{DS}'
        	],
        ]);
    }