Thank you very much DG for your quick answer.
I managed so far to go through the first 4 lines )up to add a new KF which appears at the end of the Tumeline
But then when I click on it nothing happens and I cannot enter a value in the PAN x tab in Animation.
I attach 2 screens :
Screen1 : after I set fit mode to COVER and adjusted the PAN X to sit the image on the left of the screen.
screen2: after adding a second KF ,sliding the image with the slider (this moves partly to the right) and clicking on the Key frame to set up PAN X go to the extreme right -> not possible to enter a value in PAN X . I am not sure what I did wrong
NOTE: I just realize after posting that on screen1 I had KF 2 selected when I captured the screen as the PAN X value is set to 130 in KF 1.
Correction: I seem to have managed now : I think I was confused by the cache and did not position the picture properly (I was entering the value manually in the PAN X tab whereas it seems to be very easy just to move the picture itself and let the tab adjust automatically.
Thank you Again I hope this will work.
Success! I managed to get the panorama displayed for 25 seconds, very smooth. Thank you again DG