Upholstery and egg crate type foams will not be rigid, and may not be flame retardant. EPS and XPS construction insulation foam are lighter weight, more rigid, and could be covered with batting and fabric. They come in 4'x8' sheets, but can be cut with a utility knife into smaller sizes. They are available from a big box home improvement store like HD or Lowes. Not sure if they are flame retardant. Depending on how large a piece you are mounting, I would think they may be light enough in weight that they could be mounted to the wall with 3M removeable hangers of some sort.

pls specify some details with wooden slides

Given the very large living area, the USP of this apartment, there are a variety of screens available which can be used creatively, mobile or fixed, see through, translucent or opaque, full height or part, etc to divide the spaces and yet give a free flowing look of a large open space, the light and views from the large windows.

very good looking with this budget I would like to go for it.