diff --git a/app/Http/Controllers/InvoiceController.php b/app/Http/Controllers/InvoiceController.php
index 3e9193c..12b2523 100644
--- a/app/Http/Controllers/InvoiceController.php
+++ b/app/Http/Controllers/InvoiceController.php
@@ -199,7 +199,7 @@ public static function getDueInvoices()
     }
 
 
-    public function preview($id)
+    public function preview(int $id)
     {
         $invoice = self::single($id);
         $giroCode = $this->generateGiroCode(
@@ -222,7 +222,7 @@ public function preview($id)
 
 
     // https://www.itsolutionstuff.com/post/laravel-dompdf-table-with-page-break-exampleexample.html
-    public function exportPdf($id)
+    public function exportPdf(int $id)
     {
         $invoice = self::single($id);
         $giroCode = $this->generateGiroCode(
@@ -259,7 +259,7 @@ public function exportPdf($id)
             $pdf->setOptions($options, true);
         }
 
-        return $pdf->stream($invoice['nr'] . '.pdf');
+        return $pdf->stream($this->getFilename($invoice) . '.pdf');
         // return $pdf->download($this->getFilename($invoice) . '.pdf');
     }
 
@@ -831,10 +831,10 @@ protected function transliterateString($string)
      * Generate a filename for the invoice export
      * Format: YYYY-MM-DD {invoice.nr} {invoice.title}
      */
-    protected function getFilename($invoice)
+    protected function getFilename(array $invoice)
     {
-        $date = \DateTime::createFromFormat("Y-m-d", $invoice['invoiceDate']);
+        $date = DateTime::createFromFormat("Y-m-d", $invoice['invoiceDate']);
         $formattedDate = $date ? $date->format('Y-m-d') : (new DateTime())->format('Y-m-d');
-        return "{$formattedDate} {$invoice['nr']} {$invoice['title']}";
+        return "{$formattedDate} Rechnung {$invoice['nr']} {$invoice['title']}";
     }
 }