The planner does not perform any calculations according to DIN 276

Which 25% because of the monument and additional effort? - that's what the difficulty levels in the HOAI table are for!

A remodeling surcharge of 25 percent is calculated according to §6 paragraph 2, 35 Bad 1 HOAI in the amount of 25.

I thought such a forum was meant for asking questions.

Sure. And there are answers. Sometimes they might not suit you. There is no mere guesswork or encouragement here.

I originally just wanted to know if the architect's claim is correct that she does not have to create any calculations according to DIN 275-

And I say this question comes four years too late.

That I am only now getting involved is simply because I am only now becoming aware of my father's helplessness (he has deteriorated a lot in the last two years) -

That is the first thing I see here as something real and tangible at all.

because he has only now opened up and honestly admitted that he can no longer defend himself!

Still, you cannot turn back time now. And as already said: in your place, I would have consulted a lawyer instead of the forum. That is taking action, not standing in a question/answer forum for days without anything happening or being initiated. You achieve nothing here. And about your dad I have to say: it is as it is: either you let them (the parents) act autonomously or not. If you let them act, then you must also expect to take hits and that mistakes will be made. That is the tuition fee. My father was a businessman. In his eyes, he still is. He is 82. I have the choice: to constantly patronize him, take over, take away, not perceive or observe, put him somewhere or let him live his life. I try the latter so that he remains happy. And yes: you pay the tuition fee. I would have definitely delegated a house purchase and renovation somehow.

The cost determination is probably only relevant now - after the completion of the construction. She also claims that the construction is not as expensive as we say. Therefore, I would like the cost determination. I am entitled to this - I just don't understand that.

As far as I understand, this has long gone beyond a mutually satisfactory solution in a simple or direct way, and would therefore, if I were convinced of my right and the strength/desire to persevere, seek the way to a good lawyer. Everything else here just keeps going around in circles.

The cost determination only comes into question now - after the completion of the construction. She also claims that the construction is not as expensive as we say. That’s why I would like the cost determination.
I am entitled to it - I just don’t understand that.

Why don’t your father and you add up the individual invoices paid and add the unpaid final invoice on top? Then you would know down to the last cent how much has been paid. You would have to do that anyway to check the architect’s figures.

Why don’t your father and you add up the individual invoices paid and then add the still unpaid final invoice on top? Then you would know down to the last penny how much has been paid. You would have to do that anyway to check the architect’s figures.

My father has really documented everything – and knows exactly what he has paid. From the moment things got out of hand, he also pointed out that the figure could not be maintained.
The planner just smiles and says, “yes, but that’s why it turned out nice” and asked if we really thought that, for example, changing the bricklayers would have made such a big difference?
And yes, we do think so.
But all that was ignored.

That’s why we would so very much like her cost determination.