The first step is based on ortogonal. Is another name or principal feature for Cherburg. (new confirmation of repeating clues, worried of its difficulty)
To see la Lumiere it is just to find that you have to draw a líne. Again it goes 560. Supersolution.
Started with a maze, french code, then alphabet, intrigant, science, and then maps.
You have to discover the concept of the next step, la Lumiere.
Easy, Cherburg, old name. To find the light, check the map towards Bourges. Continuing youll go Dabo. Marcher sur les eaux. Christ, cross to be drawn. (And connect the Golfe Juan clue)
Very probably to stay very connected annalizing everything from 420 as the message and image that starts the supersolution.
Then he very probably added lines, supersolution lines, very tiny clues.
He can refer to Chartres again. Jumping steps, la Lumiere of the bow problem youll be just about to have.
An important sense of taking the info out of him.
I dont want to give you the solution, I maze it up big. I will help you but not that much. You can go nuts, and I will encourage it, as I have checked possible numbers, históric and geographic lines your mínd may mess yourself about.