Rest-Api Funtion "Arrivals by Airport" returns no

I wanna display all flights that will arrive at a given airport within the next few minutes. My approach was to use the "Arrivals by Airport" Function of the Rest-Api in order to get the icao24 of all arriving flights. Next, I could use these icao24 in the "All State Vectors" Function to gather the current Position of that flight.

But the "Arrivals by Airport" returns an empty dataset, at least if the Time window (begin & end parameter) is not far in the past.

opensky-network.org/api/flights/arrival?...42000&end=1603274400

should return all flights arrival in Munich (EDDM) between 10/21/2020 @ 1:00am (UTC) and 10/21/2020 @ 10:00am (UTC).

I made this request at 10/21/2020 @ 10:33am (UTC) and get an empty dataset.

Whats is the correct Rest-Api request to get all flights during the last few hours toward a given Airport?

Thank you. Is there another way to get realtime (position) data, filtered by an Arrival Airport?

I need the positions of all Aircrafts approaching a given Airport. When I filter by Coordinates I'll get a lot of flights that are not going to the desired Airport, but cross that area. If I detect a decent I can't be sure that the Aircraft is going to land. A Decent from FL 300+ starts far away from the Airport. So I would detect a lot of wrong flights.