Merging exploded polysurface after split

hi all, I have to split a polysurface with mutiple curves on it and make contour on each divided polysurfaces blocks with the nomal direction of their top surface. What I tried at first was to make the polysrf into brep, extrude the curves, cause brep split works only with brep or surface, and use ‘split brep’, but it didn’t make the right result. (why?)
So I exploded the polysurface, and splited them with curves…but how can I merge them into several polysurfaces or breps divided by the curves?

( This part is what I tried. I wanted to make points on each surfaces, and seperate them by using ‘curve side’ with all cuves from one side, finding where the value changed from -1 to 1, and merging surfaces with same result.)