Hy guys! Many thanks for all the answers.
Yesterday is something happened!
I have watch some video from the server and have save a little Text-File on the Server, than the communication was brocken!
I have go to my server and have see, that the Active-LEDs by the NAS-Case are operating.
> But just the Slots with this bad Seagate drives!
The other both Slots (2x WD HDDs) was just a little bit active.
Shurely, the mdadm has rebuild the RAID System on the Seagates, after the Seagates has crash ...or something.
The rebuild has take over the night.
Today the system runs again. I am very relieved!
The SMART Logs are show also, that there is something happening with my Seagates.
(In the Pictures you see the new SMART-Logs!)
I buy now two new WDs!!!!
regards, Ruby