Grasshopper - Tekla: problem with generating boundry for a plate

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Hello everyone, new to grasshopper, so many questions. And here is like paradise....

First thing first, I am working on a school projet by using Grasshopper and Tekla. Facing a bit problem with the boundry of Plate. 

Now, how do I got this mess is not important, the important part is that now I want to use the triangles as boundries for plates.

I have no idea how to join them together.

so, Help?

Thanks in advance, I have so much to learn.