Reassembling: Make sure, the cable of the DC-In board is on the logic board-side of the screw hole when putting in the logic board. Otherwise the display data cable bracket won't fit in and you have to remove the board again.
So I hope, the DC-In board was really the cause of my problems. I changed the battery and the charging cable before and still had problems. At this moment my macbook loads again, but I don't know if its because of the board or again just luck. Thank you very much for the guide.