Thank you very much,
it is running again. But as already mentioned in an other thread I have defects in memtester diagnostics. During bit flip test I get a FAILURE and when a bigger chunk of memory is used like 1,8GB than the system freezes without any feedback. It seems that the DDR-memController-calibration is configured out of specs for this kind of chips.
I took the application from debian with apt-get install memtester.
By the way this was the reason to change to armbian because I could get to the sources and build teh system fron scratch, but it does not boot at all. Can I find a way to do this also with BPI-Projects in git, is there a wiki to get it build ?