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?