Thanks once again!
I took out the SSD of the machine now and attached it to my PC and can seem to be missing an "assigned" letter to some of the partitions. Here is a overview on the SSD:
This is a small draft of the files in D :
And here for E: drive:
They are nearly the same...
And I can't do anything else than "delete volume" on the 120GB+350GB partitions.
Can this be any helpful for you guys to look into?