You were right, i am not measuring any voltage on the BT-module.
I have checked the connections by using the datasheets, and watching the video.
In comparison to the datasheet of the MCU the naming on my MCU is reversed ( top down = rst, tx, rx, dvcc, stat, dgnd <=> dgnd, stat, dvcc, rx, tx, rst)
I don't know if this is due to a newer version?
In comparison to the video I have left the reset pin unconnected, could this be the issue?
Thanks already for the quick response!