The GTIN field is the field in which the barcode of the product is entered if that information exists for that product, this information is not mandatory, and the application does not return you to this field, but the cursor automatically moves to the first empty field until you remove the letter keyboard from the screen.

You remove the keyboard by placing your finger on the bottom of the screen and pulling up, a triangle, circle and square will appear at the bottom of the screen, you need to click on the triangle and the keyboard will disappear, you will see the field "Make" and you can create your item.