I just tested http://www.tracto-technik.de on Android and iOS and I am not able to observe what you describe. Here is how it behaves for me:

The parent items have 2 active areas that can be tapped. If I tap the text, the link is loaded immediately and no sub menu is displayed. If I tap the arrow, the sub menu is toggled and no link is loaded immediately or in a short while.
Can you explain how exactly you are testing this?