added some translations

01-frontend/public/locales/de/translation.json

@@ -4,6 +4,7 @@
   "freeShipping": "Kostenloser Versand ab 50€ Bestellwert",
   "inStock": "Verfügbar",
   "outOfStock": "Ausverkauft",
+  "quantity": "Anzahl",
   "rateThisProduct": "Dieses Produkt bewerten",
   "ratingFrom": "Bewertung vom",
   "review": "Produktrezension (optional)",

01-frontend/public/locales/en/translation.json

@@ -4,6 +4,7 @@
   "freeShipping": "Free shipping for orders over 50€",
   "inStock": "In stock",
   "outOfStock": "Out of stock",
+  "quantity": "Quantity",
   "rateThisProduct": "Rate this product",
   "ratingFrom": "Rating from",
   "review": "Product review (optional)",

01-frontend/src/helper/productpage/ProductInfo.tsx

@@ -129,7 +129,7 @@ export default function ProductInfo({ item }: { item: Item }) {
                 <Stack direction="row" spacing={2} alignItems="center">
                     <TextField
                         type="number"
-                        label="Quantity"
+                        label={t('quantity')}
                         value={quantity}
                         onChange={(e) => setQuantity(Math.max(1, parseInt(e.target.value)))}
                         InputProps={{ inputProps: { min: 1, max: item.stock } }}