Stadion Structure - moving points for Carrier width - Please need help

Hey,

i got stuck at the moment, i have some Roof and Stand surfaces. I Devide the outline edges to get my beam structure, but now I will not go any further. 

I tryed to move the points of my intersection on the Outline, but it dosent work. 

The idea was to move the points as wide as I need the bearers,

different lengths on the start and the end. After i create the lines i would move all points in the z direction, also here different heights. 

I Hope to create my 3D beams.  

But i tryed many ways and i don't get results. Maybee someone of you have an idea.

I would be really thankfull for some help, i kneed it for my exams.

I did something straight, but my prof want's a new way and time is ticking away....