Floor plan and extension of a house - Year built 1966

I honestly don't believe that you can renovate it for 400k, nor that you can build it new for that price. I assumed the 400k in the original post referred solely to the renovation costs and that the purchase price for the property is already excluded, right?

I am known for speaking uncomfortable truths: I consider the renovation for 400k a pipe dream. You are practically building new. You are only using the old (presumably uninsulated concrete slab) and the old (technically disastrous insulation-wise) exterior walls. Everything future must conform to these walls. So you're not saving anything.

On top, you’re adding another floor, a new roof, on the outside you’re putting every conceivable expensive climate gadget on the house that you’ve seen on Instagram.

I don’t see this as either a new build or a "renovation" for 400k.

What would be one possibility. It is somewhat sad that something like this is supposedly not achievable for 400k How would one build the floor plan? Which facade would you recommend?

Wooden beam ceilings require ample girders with appropriate supports for such spans. Or some columns. Such large, open spaces are better achieved with concrete ceilings.

To be honest, I can't imagine that this can really be realized with a wooden ceiling.