Basement extension - is a retaining wall necessary - what are the options?

Hi!

Here is the following situation for discussion: I will spare deeper info because a) it should be apparent from the pictures and b) because I am interested in constructive advice, detailed examination should be my problem.

As with all home builders, the goal was and is to be as cost-effective and sustainable as possible. So I am counting here on a "neutral" advice.

The situation is:

I think "my" architect and "his" company have their opinion. (I am not an expert. Architects and offices should be, undisputed. My decision to basement the new building and to enable an exit into the (basement) garden was maybe a stupid idea, but now it is as it is.

How a retaining wall has to be designed is determined on the one hand by the structural engineer, on the other hand by the architect and construction company, of course.

BUT: my question to you: For every square meter of basement exit I lose valuable garden. Therefore, I would now like to maximize the garden area as much as possible.

In the pictures you can see in red what is necessary (in my opinion) and in green what I can do without (in my opinion, pay attention, no static parameters considered!).

What do you recommend? As a layman, I would also consider Corten steel sheet piles as possible, the main thing is that the garden area is maximized...

Many thanks in advance for suggestions!

Here is the following situation for discussion: I will save deeper information because a) it should be clear from the pictures

"Should," subjunctive, yes. Even if my "boss" once said I am not at all a little fool: here I can only envy anyone who makes sense of your pictures. We cannot look into your head.