Add a crawl space extension

Hello to all forum members. I just registered here today and would like to ask my questions to you experienced home builders. I own a single-story building, built in the 1920s, made of bricks (18m x 8m, 24 cm exterior walls, with a 12 cm thick load-bearing wall in the middle) with a shed roof made of fiber cement corrugated sheets. Thus, a typical bungalow construction with foundation and floor slab. I have uploaded all load-bearing elements in a sketch as an attachment. The rooms are about 2.55 m high and above them is a "crawl space". At the highest point, it is 1.50 m high and at the lowest 0.5 m high. We would like to gain an additional 4 x 8 m space and plan to add an extra floor to part of the house. Thus, to convert a quarter of the crawl space into 2 living rooms. I have 2 sketches in the attachment. One of them shows roughly what it should look like. My first questions now are: Is it possible to build up the exterior walls and the middle 12 cm wall with aerated concrete blocks? How should the right exterior wall (see sketch) be planned? Is it necessary on the ground floor to build a load-bearing wall for the right upper exterior wall or can I support it on a beam that spans 3.80 m from the existing rear 24 cm exterior wall to the 12 cm middle load-bearing wall? Is the 12 cm wall, which sits on the floor slab, sufficient? Many thanks for any answers, ideas, and suggestions.

Doesn't anyone have an idea or an approach?

You need a building permit for that. And it is also an intervention in the statics. I would have an architect take a look at it.

In the forum, no one can provide you with a reliable structural calculation. For that, you absolutely need a) a building permit - which also means an architect who takes responsibility, and b) a structural engineer who confirms the load-bearing capacity and statics.

Thank you very much for the answers. I know that you need a building permit and an architect for that. I already thought that you can't get further with descriptions and sketches.