But i cant get the filter of the duedate working.
Any ideas how i have to build it?
I first tried to get all tasks and filter later but as the amount can be to big and the limit of 50 objects per call makes it even harder a filter by duedate would be great for my scenario.
You could create a saved filter for the due date, then use the Gets one saved filter call to get the data you want, I will start testing this for a better solution though.