you would need a subdivision plugin like subd or artisan for the design and fredo’s thrupaint for the texturing.
I think you could model the sofa with the native SU tools, using Scale to adjust the height of the back sections. Or, use a lofting plugin to get the curved sections for the back and Follow Me for the welting on the cushions. If you had an image of the full sofa, it would be easier to try to figure out how to model the piece.
I’d make a profile of the couch. Draw the curve in plan. Set the profile perpendicular to the end of the curve using CLF perpendicular face tool
Select the curved line, click the Follow Me tool, select the profile.
Turn on hidden geometry and edit/modify the one end using the line tool or
Make a horizontal curved face and place it properly to intersect the couch extrusion. Run intersect faces. Erase the parts you don’t want.
If the model is not used for manufacturing, cheating is the best way. Make a rough and blocky approximation and use textures for the plush appearance.
thanks guys, how do you create a face with this two lines? 
do you know where I get the thrupaint for skp 2021? I cant find the link
Most of Fredo’s extensions are on the SketchUcation Plug-in Store.
https://sketchucation.com/forums/viewtopic.php?f=323&t=44552
Fredo Curviloft --loft by spline or other Curviloft or TIGs Extrusion tools. You may want to add connecting curves or edges depending on the technique used or desired end result. Simply with loft by spline the face will have straight edges connecting the ends of these curves.
thank you that was very easy!!! Iam just annoyed because thrupaint is not working anymore, wish sketchup could incorporate this option as default in the next versions, because who work with sofa designs its impossible to add texture in curved geometries.
You can’t use Projected Texture?