Simplify mesh faces

I got this mesh from ngon mesh from polylines,
I am trying to make mesh topology vertics
the mesh should be tringular with only valance of 6 but in the vertex vertex structure it shows 3 and 12 not 6.
I deconstructed the mesh and created surfaces and found out that there are 3 triangles inside each face.
is there a way to merge these 3 triangles in on face?

Hello - please post a file with the mesh.