About the 6B navigation screen.

It sounds like what you are seeing are the Navigation Prompts pop-ups.

As you approach an intersection (while following a Course), a pop-up will appear telling you when and in which direction to turn. If you have it set in the activity profiles to Text only, it will overwrite your 6B fields at the bottom of the screen.

The pop-up should disappear automatically once you have ridden through the intersection. You can also dismiss the pop-up by pressing the Back button (lower right button).

Thanks for these informations.
I'm sorry, I made a mistake everywhere, it's not screen 6B which displays very well but navigation screen 2 (fields) which I don't see with my own choices.
I understand that my current settings overwrite screen 2 because of the option: Text only.
I found in Menu > Settings > Activity Profiles > (for me road) > Navigation > Map and if I'm in the right place > Guide Text.
When I click on this option I have three possibilities:
1/3 during navigation;
2/3 Always display (current choice)
2/3 Never display.
There is no information in the user manual; both in the English and French version.
Can you help me please ?
Moreover, if I choose one or the other option, will I still have the indications of the street names or to turn 150 meters to the right in the upper part of the screen?
Thank you for everything.
Cordially. Terry.

Try experimenting with the different options to see what suits you. I prefer “Never” so the only prompts I get are from the course points embedded in TCX or Fit courses that I’ve downloaded from RWGPS. However, you won’t get the 150m Garmin generated prompts and street names with that option.