Thank you, this time I managed to get the command to work with administrator rights.
defrag c: was a pre-optimization information on disk space (see photo). No other information followed for the 10 minutes I waited, after which I closed the cmd window, as no further command could be entered either.
SFC scannow: apparently after checking 100% it found no integrity issues (see 2. attachment)
After this I re-tried windows programme defragmentation and optimization of c:, which resulted in process being re-directed ( 3rdattachment).
Can you make anything of it?