I’m so sorry for my mistake, but gomezz gave the right hint for the solution: the first item in list is the first item in the queue 
Continous play works from top to bottom and not from bottom to top - that is clear and I was on a wrong way because my play-order and sort-order of podcasts was wrong (newest on top, oldest on bottom and wish to play from the oldest to the newest one). Now, by sorting the other direction everything works fine!
Distressing, that I made this mistake! 
and thank you all for your answers!