Strange things are happening ....
I followed the advised Apple procedure now 3rd times.
The first 2 time no change at all: no sync from watch to Fitness App (but in health data you could see the data, etc....).
I've tried now exactly the same a third one ... and hurray: did two bicycle outside workouts and a walk outside workout and now I have all data incl. GPS maps in Health and in Fitness App! And also RunGap is able to import it from Health again with Maps.
Only thing left: all older workouts only have the starting pin and not the full route and one running workout from 2 days before is now missing (I see the data in Health sources from the watch) but its not seen by Fitness App nor by RunGap - but ok...