Any idea for the catia design of this pic ?
I'd start by sketching a framwork of the shape.
Ignore the fillets, wall thickness, and open area for now. Just work on the base shape.
It can help to draw on the part with a marker if you have access to it, and not just photos.
Hopefully you have the part. Making this without being able to take measurements would be less enjoyable.
A simple version of such an outline is shown below. It would need more profiles and guides to be finished, but hopefully it gives the basic idea.
From there, start lofting, or otherwise filling in the open space. I'd do it in several steps rather than trying to force everything into a single loft feature.