Surfaces to brep

Hello All,

I am trying to do boolean-difference from a set of breps onto a collection of surfaces, but i am not allowed, I try to place the surfaces, that technically should compose a closed solid, into a brep collection component but this doesnt work either, if I extrude the surface and use this to boolean-difference onto it works (but this doesnt work for me because the extruded surface bends under itself and the surfaces cross over, not possible if this was to be a slab).

Is there any way to make the collection of surfaces become a true brep that I can boolean difference?

note: In GH blue is collection of non-brep-conforming surfaces; on purple working but invalid bolean-difference.

Thanks in advance

facundo