oke, my idea is now, convert the spirale with "convert selected objects stroke to path", now i can place a new surface out of the spirale as in the following screenshot:

Thanks for the answers. maybe its possibile to draw the path different from scratch, so the problem can be solved different, i will try a bit.

Hello, i cant join two selected nodes of two different objects, one is spirale(object is converted to path) the other bezier.
My goal is to set a fill color for the whole thing. Here are some screenshots.
Many thanks for answers!

hello again, its a bit complicated to adapt and i want to finish it soon. so i tried some other operations to just merge it with splitted parts, but:
how can i cut of the stuff behind black square without destroy path integrity of the right visible?

Many thanks! with this example i play a long time now

Hello! I made a text where some parts are overlaying others, i dont know what way is the right one to overlay parts of the same path over it self. i think i could just make a clean cut into it but its complicated. my solution to overlay it just with a white square isnt good cause i get pixels if its...