Start with super straight and flat wall studs and the $$ premium that that will require. Then the $$$ premium for the plasterer and the double layer of upgraded stock.

OSB board will do the trick. You need another photo for us to offer a species and finish. Natural finish (clear coat...water based polyurethane finish...NO oil modified) in a low gloss or satin finish on white oak with FLOOD LIGHTS will offer the same "look" as the poor photo. Beyond that, you will need a better photo.

Well I'll try to make a 3d of the room and upload it. But that will take some time. Thank you :)

Hello, I feel that you can design this bedroom by having 1 opaque wall at the back, and 3 transparent walls using glass & steel or glass & wooden french doors. The walls should be white, with minimal accents of blue or green, use 2 layers of curtains with sheer, and brass hanging lamps. All doors can be white PU paint. Waterproofing this bedroom will be essential, so make sure you have sealed all joints and surfaces, with a minimum of 2 feet roof overhangs. Hope this helps! G