Hmm that wasn't the solution.
I tried to:
1. Both cards, very card connected to 1 seperate monitor
2. one card in pcie slot 2 ( orange x4 )
And always the same the second card goes at full fan speed from the start ( yes I swapped them too and everytime the one at bay 2 ).
If there is only one card at bay 2 it is the same
without a picture output at the monitor!
I downloaded the ( more ) detailed manual that says I have to use a connector
Anyway thanks
I thought for just mining there is no need for a bridge but oh well