I am a beginner and don't know what is this, may be a compound (if that's what its called)?
I am trying to extract those shapes but do not know what and how to do with this one.
There appears to be a clipping mask.
Select the Direct Selection Tool (the white arrow) and click-drag on one of the bottom corners of the artboard -- being sure to NOT drag over any of the artwork you see.
A rectangle will probably highlight. Simply hit the Delete key twice to remove it.
Select all. From the menu choose
Object > Clipping Mask > Release
You should then see your artwork and a bounding rectangle around the artboard. You can delete that rectangle, but even if you don't it will stop acting as a mask.