Méga CGR Colmar

--- We talk English, German and French. Puzzles contain no text at all ! --- You are trapped with your colleagues in an abandoned worksite. Who locked you up and why ? But most important : how will you be able to get out of the building ? A few hints will allow you to find the daylight again. But be careful, once you have left the cellar, you are still further away from the light than you think ...