You are most likely seeing this login prompt because you are trying to access the HaWo Waschapp from outside the HaWo network.

Make sure that you are accessing the website from a device connected to the LAN port in your room or from within the "STW-Students" WiFi, where you are logged in using your personal login data.
Accessing this website externally is possible, if you have logged in from within the HaWo network once.