How can I draw/create the wavy lines in this way?

[TomTom66]

Hello, maybe someone can give me some tips: How can I draw/create the wavy lines (see images) in this way? I have already tried it a few times with the "Pen Tool" but somehow the line always becomes a bit "angular". In addition, it seems to me that it should actually be more like 2 filled (wave) shapes which are then assigned different transparency and which partially overlap.

However, the image ("shape") must also be rounded off at the bottom or at least cut out so that you can later use any image as a filling.

Is there something like this in the Xara design templates (or in the case of free templates, vectors) that you can convert. But I found nothing.

I have been using Xara for 15 years but only for graphics/websites. Unfortunately, I have almost no experience with drawing such curves,

Thanks for any help.

Tom