thanks for you reply. I think it will be very helpful.
I have a follow-up question:
What will be the best-practice, if you use HP OO and HP QC (respectively HP ALM) together?
I already learned how to integrate them, technically; but how do I use it? Get a certain release, get the related requirements -> test sets and tests itself and then finally I execute some tests with the help of HP OO flows and after this, set the new status?