Thank you FraPre for a wake up call...

There sure is a lot to learn. 
I have now  made 2 "happy" landings.
Before T/D I set a new altitude ZERO and    kept VNAV button activated during descent.
When close to the airport I went for LOC  and  airport  within 10 nm  I pushed  APPR.
During one descent I used the speedbrake - perhaps 15 sec. to prevent overspeed.

In the other test I changed data for a waypoint that was 331/12300  to 280/12300

VNAV was turned of autom..

Maybe I have have been totally wrong - but it turned OK for me.

Thank you